Spin n Go have an addicting quality. I too find myself start playing one or two just for the fun but then it gets serious and play a ton of them.
The level of fishes in them make it seem like its super profitable game. Winning some jackpots here and there getting a 4x 6x multiplier seems also like a good bang for your buck and some nice easy money.
Before you know it, those AJs versus J3o bad beats may get you in a mini tilt or all those up and downs would leave your bankroll the same, so why not play an other one? Until your bankroll start hurting. And move up in buyins to chase losses.
The best option is to not play them at all, but since they are so addicting what I normally do is change to play money. The point here is if you cant stop playing at least not lose money.
For when to stop other than spin n gos, I would say if you are tilted, tired, or start losing and that is getting under your skin.