Here's the thing: If you're thinking that you should store them til 2050 to hypothetically "cash in" for a museum.... but you don't know if they work today, you don't know how to fix them if they don't, they haven't been gone through and brought back to best original standards today, etc... then why do you think in 32 years, they'll still be viable because you stored them in climate-controlled storage and valuable to cash in with a museum?
Short answer? They won't be. Long answer - even if you do all of the above, as I've described... they won't be worth that much. Realistic answer - even if their value goes up 30x what it is now, and you are the last person on earth, of the millions of items sold of each, who has these working.... will they even be worth what you have paid to store them all these years?
Best bet? Sell them now. If your C64 fires up and works, figure $100 for a full system, likely more if you have working drives and a small software collection to go with (more if you have a large software collection to go with - and don't forget to check that collection for desirable/collectible games!)
The Timex Sinclair 1000 is a great little piece, and has historical significance, but realistically? It's desirability in people's collections is virtually nil because it doesn't DO too much of interest to today's world. It's an oddity, and cheap enough to have in one's collection to say you have one, but it's that piece that will rarely, if ever, get off of the collection shelf. That's why they still sell for nothing despite their historical significance.
The Mac? I'm not too up on those. I know that there's a lot of issues with caps on certain series. Also battery leaks. Working, it's value is probably around the same as the C64 collection. It may go up. Probably will. But not a a whole lot. Best bet to "cash in?" Sell it now.
Sell them all now. Walk away without worry, with around $200-300 in your pocket richer for a quick find that you don't care about.
OR... better yet. Learn them. Use them. Love them. And dive deep down the rabbit hole that is vintage computer collecting like the rest of us