Hi everyone!
Iam building a browser-based idle RPG where players gain XP and resources even while offline. The problem I am running into is stat inflation after a few weeks; early balancing falls apart; with some players reaching levels / DPS so high that new content becomes obsolete almost immediately. 
This also discourages PvP & new player engagement.
I have tried scaling XP requirements exponentially and introducing soft caps but players still find optimal loops that break progression over time. 
I am wondering if there are better design patterns for long-term stat growth control in idle or AFK-focused PBBGs like decay systems, prestige mechanics / resource conversion models that limit runaway numbers without feeling punitive. Checked How to make an Idle game or incremental game? - For Beginners - GameDev.net Salesforce Administrator Course guide related to this and found it very helpful.
How have others managed stat growth and game balance in persistent games that are expected to run for months / years? 
I would love to hear what systems have worked (or failed) in your own games & how you approached the challenge without killing player motivation.
Thank you !! 