What is the maximum number of missions/a decent cap?

[SunlitZelkova]

If I constantly flew missions and never deleted debris, at what point would it start to impact performance in a noticeable way?

EDIT- To clarify, I mean flights/spacecraft/objects, not contracts

Edited April 20, 2021 by SunlitZelkova
Clarification

[OHara]

Having many craft and bases in your savefile only makes saving the game take a bit longer.  KSP only simulates physics for craft within about 2km of the craft you are piloting.

I have 'persistent.sfs' files around 5MB that cause me no problem.   I think size of the save-file is a reasonable measure of the number and complexity of the craft in flight.

If you keep the game running for a long time (hours) in one sitting, though, @Anth12 has noticed that KSP gradually uses more and more memory, and that problem is worse with a larger save-file (link to bug report).   At some point the operating system will slow everything down while trying to keep so much memory available to KSP.

[Anth]

In my experience its more about the loading times than performance in game now.

Garbage Collection issues for memory used to make the game glitch/stutter, the more ram used the more the glitching/stuttering happened. (Garbage Collection is how Unity deals with cleaning up ram, and does a pretty bad job when loading a game save. Subnautica which also uses Unity loads its universe once so its not noticeable. KSP loads the universe a lot so it becomes obvious)

Garbage Collection performance issues aren't an issue anymore in my experience, but I am not sure about others experiences with slower computers.

Loading Times initially for bigger game saves is a little longer, but the load times will get longer and longer very quickly if you are changing scenes a lot regardless of how much ram is available

I haven't experienced running out of ram with KSP running so I am not sure how badly it performs when that happens