Not necessarily easy. I can put up with bad material if there is prior evidence of good music. I have unstanned GOT7 and Highlight, but that was caused based on the fact that GOT7 music started to become unremarkable and I started to dislike a lot of their earlier material that I previously liked. I haven't consiously unstanned Highlight, but I have drastically stopped listening to them and no longer have them in my stan list..
Edit: I've said this on akp, but I should say it here. I consider stanning to be an arbitrary concept that different among individuals, thus my stanning will probably differ from others..