What to do when completely done with your project?

I have 5 projects that I'm completely done with and what do I do when I'm done? I want to save them on my external drive and if for some reason down the road i want to come back and do a re-edit etc. I don't want to look at old projects all the time when I'm doing a new one. I'm afraid if i keep adding up projects the program will glich or crash or not run properly? Do I just export or move the projects ? Can I bring them back in for a re-edit?

Basically whats the proper way?

Thanks,

Preston