Wow - another perfectly innocuous topic pulled totally stage left because people didn't bother to read the question and instead twist it to suit their soapbox.
I do think 2 months is a reasonable time. I have way too many sources and different types of music to make a quick decision. It's not usual for me to change something out and be initially unimpressed. Then, 6 weeks later - out of the blue - a new note or nuance to a song or record I know well - or a sensation of being there that i hadn't had before - and I'm satisfied. I got to give it time.
What I am not as good at is NOT noticing a change. Once the time goes by and the component is integrated, it usually stays in. I think your calendar idea is a good one.
I considered at one point putting together a test set list - maybe 10 songs I would run through after a change. I maybe got to #2 and lost interest.