10% or less of the time. I've bought and assembled 4 "enthusiast" PCs for myself across the last 12 years, each time time making a multiple-generation leap in hardware. Actually, I had little choice but to replace the motherboard with the CPU each time, because the march of technology had pretty much rendered my old hardware obsolete each time.
I've also bought a dedicated file server and a used "enthusiast" PC that I could dedicate to CPU-intensive tasks.
I find it amusing that people are trying to argue that there are other enthusiasts out there beyond the ones trying to build fast, powerful hardware. It's like saying that there are car enthusiasts out there who aren't trying to build fast, powerful vehicles. I'm sure they exist, but for every one of them there are at least a dozen others doing doughnuts every night a few miles down the road from me, flashing their illegal lighting modifications in an impressively gaudy display of car nerdery that, in my mind, invalidates any and all criticism they might have over my hobbies.