Which Threads Get Used Most and Least on a Serger?

I use a serger on which I switch threads, usually for colour, far more often than I like. I’ve never kept track of which spool I put where but have finally noticed some are thinner than others on how much thread remains on them. I mostly do just the general 4 thread serging with upper and lower loopers, then left and right needles.

I don’t think the threads feed through at the same rate, seeing how some threads criss-cross on a serged seam, and some just go straight. Can someone please tell me which threads get used the most, down to which the least, on a serger? I’m going to start rotating thick and thin spools every time I need to change threads so I can go through spools more evenly.

Thank you.