How long can radio modules retain custom settings?

I own a few of the HM-TRP uart radio modules and have successfully programmed one for higher speed. I noticed that when I disconnected the power to the module and then powered it about 5 minutes later that my settings are still intact. My power supply is 3.3V through an LM1117-3.3 regulator with 10uF connected to input and 100uF capacitors connected to output. I don't think their values are high enough to cause data retention. and the only other capacitor I used in the entire circuit is 47nF.

This suggests to me that these modules have special kind of ROM that allows long-term storage, but the question is how long would such storage last for before the settings are automatically reset to defaults?

At least 10 years. Typically between 20 and 100 years depending on specifics of the EEPROM or flash used. Higher temperatures reduce retention time.

Nor will the settings reset to default. What happens is the stored data gradually gets degraded and corrupted. It won't just gradually, or instantly return to an erased state any more than a 300 year old piece of paper will gradually, or suddenly become blank. The ink may fade and get spotty but the paper will also develop dark spots. You'll get ones turning to zeroes, zeroes turning to ones as well as invalid states in between.

If you ask the supplier or manufacturers for a datasheet, or even just google then you ought to find how the modules work regarding settings, sounds like they have an eeprom.
As mentioned non volatile memory lasts a long time, longer than the life of an average piece of equipment.

I googled the datasheet and I'm still in the dark as it's writen in Chinglish and totally confusing.

Mike.