There are two types of resets that may occur on the server:
1) Routine Server Restarts. These restarts occur in 8-hour intervals and do not get rid of anyone's progress prior to the restart. This is just to ensure that the server does not crash and does not have too much lag. You can check the next restart time by running the command /restart time.
2) (Very Rare) Entire Server Reset. These resets involve an entire color server being reset (i.e. Player World reset, Pokedex reset, Gym Progress reset). These occur on rare occasions, and there is not ETA on them. If you purchased a rank on that server, you will keep your rank. Any purchases made within the last 30 days of that reset will be refunded. Once again, there is no set date for resets.
If you have any questions, please feel free to let us know and we will gladly answer them.