I use a DM map rotation of 55 maps, with about 15 others that get swapped in now and then. So I play 70 DM maps regularly.

I have a couple of thousand others that I downloaded to see if I wanted to put them on my server. I don't use them, but I keep them around to remind me that I've already checked them out.

i think i have more than 10.000 if you include gamemodes other than DM/Classic
one day when i end up in hell or heaven i'll sit on my pc and sort them all. but till then, only 100 or so have been sorted out lol.

i have an Excel sheet where i put info on all the ordered ones, same for skins+models, voicepacks, gamemodes and mutators, etc. but i don't really have the time for this. the way i sort the maps is simple: delete the one that i REALLY dislike, fix the ones that are broken, assign them a category/pack, etc. for example all the original maps are under "Original"; all the Unreal ones are in "Classic", etc. then there's an arbitrary size column, name, a "Done" check (it means the map is complete/ultimate, nothing left to do) and a "Note" column (for example, a map can't really be played with bots so I'll type it there [maybe too many jump pads or simply can't be pathed]  or "add a lift exit here" or "fix the bot pathing, remove shock" etc)

i have no way to count how many maps I have (multiple installations + if i select all in the archives it's gonna select read-mes too etc) but it's more than 8k, 9k for sure