It seems like we will not find common ground here. First off, yes I have struggled with incomplete sets and worked for a long time trading with others to complete them, some even taking me over a year.
Not all care to complete collections, there are some sets that I only like one print from, but I choose not to collect them since I prefer complete sets. Not all share my view and there are some collectors that will only collect prints with cats, regardless of the set.
The point is, some of us do not see this as simply a game where the goal is to complete sets. I like to support the art I like, and when it is sold out, many users make more sets! This is where their revenue can continue.
The point isn't just to "catch em all" but also encourage the artists you discover here by collecting their work.
From someone who has been on this site for quite some time, collection and artist support has been the spirit of the game. Not completing sets for the sake of completing them, and trying to force those that have the prints you want to hand them over if they haven't logged on in "X" amount of time.
If you must complete every set you have, then perhaps you should just trade away the ones you can't so others can complete their sets? With the print counts uneven throughout all sets, there will always be someone that cannot complete their set, regardless if users are active or not.
Stop trying to force others to give up what they collected just because you do not feel they log on often enough.