How many 'permanent' Pokemon do you keep?

Around 600.

My 'permanent' collection is 480. I have 650 pokie storage, and I never let my free space go to less than 100 at the end of the day. If I have less than 100 free after I clean out the trash, that means that I have more than 70 ready to evolve.Since I evolve about 68 per session, it's time! I want 100 free when I start every morning, because I can catch that many on a rare good day.

My total storage is 700, and after a mass evolve & transfer, I have around 590 keepers. Storage was starting to get tight until the gym rework, when I was able to transfer a lot of redundant prestigers (Wigglytuffs, Lanturns, Sneasels, Cloysters, etc.). I still have a surplus of Laprases and Snorlaxes, but I'm waiting for a double candy event to transfer the ones I don't need.

800 Storage

About 700 left after a typical purge. I keep the best of each unevolved type, sometimes one or two more with good IVs, then purge the rest as I wait for my next use of a lucky egg.

I also keep the best of each evolved type and any others that may be useful someday, someway.

Finally, I have about 100 dratini and about 50 larvitars (and a few more important or rare types) waiting for the next double candy event to be transferred.

600 and bought more 50 slots.

850/1000
Because I still have tons of Dratini and Larvitar in case of Double Candies from transfer, LOL.
I don't need their candies now (need dust moa), so I can keep waiting...

My box is 800. About 120 of them are vital after a complete evolve session. If I only had that 120 my game play would not change.

I mean I really do not need 10+ Magmars, Jynxs, Electrobuzz, etc. Many useless mons like Stantler.

I hoard Magikarps, Dratinis, Larvitars, Mareeps, Totodiles etc to send to professor when there is double candy.

I like to put Chanseys on gyms.

I think this was posted already, but a really good tip is to nickname your Pokemon. I know it's a bit lame, but if you nickname all of your Pokemon AA, AAB, AABC, AABD, AABE, etc, you can sort alphabetically and your best mons will all be at the top. I would've suggested by favorites sorting, but I favorite all of my highest IV attackers to evolve for next "good" event. Best of luck!

About 700 of 1K. I don't use all those and many are 95%+ unevolved versions for future (possible) use.

Knowing what I want to counter with plus alphabetic sorting makes it easy to grab what I want. I do wish we could set up individual squads though.

I favorite all of my best attackers and defenders and then sort by Favorite when I want to battle and/or add to a gym.

I still haven't brought myself to get rid of all my prestigers, so I have more in my PokePouch than I need to.

Got 115 so far (1 of each species except 2 rhydons, and keeping Eevee even though it's not a different species). I plan on having every male / female and other variation of mon, but not prior evolutions with the exception of eevee. Will upgrade bag in the future, currently still standard bag.

My top ones are always at the top, so those are which I use in battles. Plus nicknames and there's always the search function.

941/1000. I try to keep 50-100 free slots before going out. All defenders/attackers are in top of CP list. Before matches (especially raids and multiple matches against the same species) I tag necessary mons with favorite and then sort by that.

Just upgradedy box to 350. I keep around 250 to battle with and for trophies. Needed space to do mass evolutions. I name the good ones by attacks and ivs and use the search bar when starting a battle.

My storage is 550, I'm holding 48 of the eevee evolves and 22 Exeggutors. Those make some sense, but why 7 Wigglytuffs from 1550cp to 1450cp--I've used a Wigglytuff a total of 5 times.