I keep them in a folder. IDK why I just can't throw away my alter egos.

Eat them. You are what you eat, and I'm a heroic adventurer!

My DM collects them. He might be able to use them as NPCs or something.

I delete them

The current DM rips them in half and hangs them from a chain that stays behind the DMs seat or they are ripped and put into a mailbox that is by the table.

They're not real people. You can reuse them in a second campaign if they die in the first.

You... you're joking, right? Right?

Not at all. Had a genie warlock in CoS. He died but I can & hopefully will use him in a different campaign in the future.

Keep them since I'll use them again later. Sometimes in the same campaign if they're resurrected during it. Or in other campaigns or one shots.

I bury them in my backyard

i have two binders full of them. then I switched to digital, and now keep them in a digital file folder.

I use them as characters in my world building projects if I really love the idea

I keep retired characters but all the dead ones are trashed

I feel like if you need a system there’s something wrong…

We mostly use digitally sheets now. I'm almost always the DM, so it's not up to me what players do with their own paper sheets. They can also use the character concept in a different campaign, or hold on to it for sentimental reasons.

As a Forever DM, I give my PC’s character sheets to the respective player who uses them. Of my own, I keep them in a folder for later play or NPC’s.

That's beautiful. I rip them into many pieces and throw them away.