I don't often check or replace the desiccant. Mostly, I use Rice along side it (in Tea Bags).
I've never had trouble with ABS and have been using PETG for only a short while - no problems (except for tweaking print process to eliminate strings).
I just installed (this week) a new V6-all-metal Hot-End to further develop a good process for PETG...
PLA generally starts breaking shortly after it sits for a couple of days. There are many posts on net about this issue - some bake it in oven... some do other things... I tend to not fuss about it and toss out about 1 meter before printing.