Hello
I am using Arduino Nano 33 BLE with RTC module DS3231. Arduino and module are connected to the power supply all the time.
Is there any suggestion on how often should I replace the CR2032 battery inside RTC module? It was my first time using RTC module and I put it in some hard to access place so I would like to change the battery as few times as possible.
Hard to say exactly but it could be several years. It is similar to battery for PC BIOS.
I purchased a few DS3231 from the Far East 3/4 years ago with a soldered button battery and they are still ticking. May be they are rechargeable - I did not even bother to check to be honest 
Op really needs to check this as trying to charge a non- rechargable type cell could end in disaster.
There are details on the web on how to remove the charge diode from the modules.
yeah, if you remove the battery from the module, you need to replace it with one from the same type to be safe.
I wonder how many modules ship with a LR version? And how many people know about this and happily put a CR in without modifying the circuit?
Thank you all for answers. It seems it was running a whole year on wrong battery type. I will change it asap.
That cannot be answered accurately however I would expect about 10 years the shelf life of the battery. The whole life thing depends on how much the battery is used verses the system power. The more the battery the shorter the life. The RTC modules generally draw in the uA range.
Hth:
" [DS3231: CR2032 vs LIR2032] Warning! Is your module killing the battery?
inside:
" Attention: Modules manufactured with DS3231 and an EEPROM memory may be for a different type of battery, maybe LIR2032 (rechargeable) instead of CR2032 (not rechargeable)! "
The CR2032 battery in a DS3231 RTC module can last several years but consider replacing it every 3-5 years as a precaution. 
What does your DS3231 module look like? If it's a ZS-042 module with the extra EEPROM chip, then it has a battery charging circuit which may or may not be populated. But even if it's there, I don't think it makes much sense to buy an expensive rechargeable LIR2032 battery. The better solution is just to cut the trace that connects the charge circuit to the battery.
The RTC will draw no battery current so long as it is powered at the module's Vcc pin, and if the module is always powered up, a regular CR2032 will probably last close to a decade.
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