Care for your MüB.
The most important thing to any fine instrument, up there with how well it's been built, is how well it's taken care of. It should be a fairly straightforward process. Instead, it's pretty clouded by misconceptions. Let's clear the air.
Cleaning your bass is the easy part: use a good product made for the instrument you own. Finished wood and unfinished wood require different products. With lacquered/coated wood what you are actually cleaning is the finish - nowadays mostly a chemical product. The purpose of cleaning this kind of surface is to wipe off sweat, dust, smudges, fingerprints, lipstick marks, beer spills, Hello Kitty stickers and such.
Unfinished wood, instead, needs to be nourished too. A maple fretboard is usually lacquered, so the above process applies. Otherwise, chances are that the fretboard wood is fully exposed. Take the habit of waxing it or oiling it every time you change strings. If you are a J. Jameson worshiper, please set a date on your calendar. How often really depends on how humid or dry your environment is and how much your fingers sweat. Probably every couple of months is a good starting point.
Which leads us to the next and way more important topic: humidity.
"My country is very humid/very dry".
It doesn't really matter what the climate out there is. Your bass doesn't know whether he (or she) is in Scotland or the Death Valley. 'Climate' is the environment in the room where the instrument spends most of the time - a.k.a. Relative Humidity (RH).
Without getting too technical, it is widely accepted that, wood is ready to be used in instrument building when its moisture content is between 6% and 9%. Throughout the building process moisture from glue is allowed to dissipate and wood is kept at ideal RH. Which is one of the reasons why fine instruments require time to be built.
Then the instrument travels to you and settles into your environment. That is, your RH.
RH is greatly affected by us. When we turn on the heater in winter, (or the air con in summer) we artificially change the humidity level, lowering RH. Wood must balance its moisture level to the RH of the environment it's in. So it will absorb or release moisture until a balance is reached. How quickly and how far is the crux of the matter.
Very high and low humidity are both bad for wood. It seem though as if the most common problems come from low humidity. Why? Maybe because the scenario described above is more likely to happen than us purposely turning our room into the rain forest. (But we'll talk about high humidity too).
When humidity suddenly nosedives, fret ends sprout out, wood starts cracking, an exposed fretboard flexes and twists trying to free itself from the glue as it shrinks. This will continue until the wood has found an equilibrium. In the process the neck might starts twisting under the concerted action of shrinking wood and string pull. You don't want any of that to happen.
Here's an important digression: Fret end sprouting is your friend. It tells you that your RH is out of whack and you need to do something about it before things get out of control. It's also an easy fix - more on this later.
To prevent damages to your instrument due to low humidity you need: 1. A humidifier. 2. A hygrometer. The latter tells you what the relative humidity level is, which is more valuable than what The Weather Channel says about your area. The former makes sure the humidity in your room stays at the right level, which should be about 45% give or take a few.
Humidifier and hydrometer. You need them. Go get them.
Keeping the instrument away from the heater is also a very good idea.
Understanding RH helps us deal with high humidity as well. Anything above 60% is not good, especially if such a level is kept for months. Above 80% you are in danger zone. The wood will swell, bend, twist, glued areas can come loose. Nothing pretty there.
Keeping the bass inside its case with silica gel bags helps. Replace the humidifier with a de-humidifier. It's all about keeping your RH in the 40-50% range.
Both D'Addario and Dunlop sell products that promise to keep humidity in your instrument case at optimal level.
Another important point to understand is this: string instruments made of wood are not all alike.
The fact that, other basses sitting in the same room for years are (or seem to be) fine is no proof that the RH is OK.
If even just one instrument shows signs of high or low humidity induced problems, then your RH is not OK. It simply means that one of them is more delicate and sensitive to humidity swings.
An instrument that was sprayed with polyester/polyhurethane is a lot more insulated from RH than one that was hand rubbed with oil or similar finish compounds. The latter is more akin to a violin or an upright bass than the former. If you have purchased such an instrument then you need to change the way to think about and take care of it.
Hopefully, reading this has clarified the true nature of humidity-related problems. At the very least we hope it has conveyed a sense of urgency. There's so much literature on the internet. Just do a simple search: 'dry humidity guitar' and you'll see. Read as much as you can. Know your enemy.
Remember, once you take charge of your bass its destiny is in your hands.
Thank you for reading. Happy playing.
ps: Fret Sprout.
Sharp fret ends sprouting from the fretboard is a clear sign that your RH is too low. By now you know how to fix it. Still, lets' dig a bit deeper. For one, this is very common and nearly unavoidable if you let your RH go hi-wire. No matter how well you instrument was built, no matter how much you paid for it, here's the bottom line: wood shrinks, metal does not. Keep your RH in check and there will be no fret sprout. Ever. It's really this simple.
Some suggest that, clipping the tang when fretting eliminates the problem. While this technique does reduce the issue somewhat, the fret itself can still sprout. To completely avoid that, one would have to round-over the fret ends together with the board edges so much so that one might end up with a worse problem - outer strings slipping off the board when playing hard/playing legato/bending and such. Besides, fret sprouting is a sign that something much worse is happening to your fretboard. It's a useful warning sign. So, again: keep your RH in check.
If fret sprout happen, here's a fix: Take the proper tool and file the sharp edges till you don't feel them anymore. Done. Really. Any repair shop can do this in minutes.
The added benefit is that is permanent. Next time your RH drops the fret edges will not sprout anymore.
Lastly, if you're wondering what the proper tool for this looks like, have someone experienced do the job for you.