Hoping this is the right section.
For immersion, I’d like to have the marks your bullets make when you shoot an object stay until the “level” is completed (they currently disappear after a few seconds). Would this have a significant effect on performance?
For the sake of context, let’s say there’s 50 players, all shooting things, for an hour.
50 players, yes definitely lol.
I mean this is real easy to test, why don’t you just spawn thousands of bullet decals and find out at what number it starts to lag.
That’s a good idea. I’ll give it a try once I finish building the map completely.
Do you think there would be a way to mitigate the performance hit?
Thanks. 
Let them fade away after a while … the last thing you want to do is have to have your players have a monstrous rig and then have a large portion of that processing power be consumed by permanent decals.
Most AAA games don’t leave their decals for ever … so I wouldn’t worry about it too much.
Probably not. It’ll be very, very drawcall heavy having all of those decals everywhere. Maybe consider making clusters of bullet holes to fade to after a certain amount of time, to reduce the amount? It won’t be accurate to what it was, sure, but it’s better than having every single one rendering separately.
Alright. Thanks for all the tips/advice guys. It’s very much appreciated.