I am more of a need-driven guy than most of you, my motto is "if it ain't broken, don't fix it". I clean up maybe once or twice a year, in general following a major content patch (or a catastrophic failure of my wow hard disk
).
Cleaning up means beginning from a fresh wow install and reinstalling everything from the ground up in the course of several days, I have pretty much a set list of basic addons that I selected based on their ability to withstand time (BT4, Grid and plugins, ag_UF, MSBT, Fortress for LDB display, BigWigs, Recount, Omen, Satrina Buff Frames, Power Aura, Mapster, SimpleMinimap, Aloft...) and afterward I add the fluff on a need-based basis, which means if I notice a feature I miss I look for an addon that does what I want and install it (or code it if I cannot find it).
I find using a pre-made UI is not for me (actually never downloaded one), I need to know what I install and how I install it and what features are activated and why, I am a control freak that way...