Why not just make it not accumulate time when the game isn't running?
With the way it's currently coded, it's agnostic to whether time is or isn't passing, and is instead based on run-start clock (to prevent tab throttling/simplify offline calculations).
I *could* do a check based on last save time as well, but I don't want to introduce more complexity to the code that could result in more bugs if needed, whereas coding a cap would be quite simple (and toggle-able, if anyone suddenly changes their mind and decides they want their offline time for the run). The game is generally balanced around having a 2x to 5x multiplier per reset atm. I could also make a configurable cap as well, now that I think about it...