Any hassles with vintage after purchase that one should be aware of?

[tough]

I apologize for a thread that may seem useless to many, and I would appreciate if people can help me realise some things before venturing into the world.

I certainly appreciate a vintage watch. The history, faded inserts, and patina are very charming.
I am still reading on many things, but have one primary question.
If I am able to locate the perfect watch for me that fits all the criteria and tick the boxes.
Does one expect to later have issues where he will need to source something that will be hard to come by?

Basically I mean. After purchasing a nice vintage piece, other than servicing and of course wearing with care, what else can go wrong which will cost a lot of money and also be extremely difficult to find?

What things are common to go wrong?
I have seen very early sport model rolexes (50+) year old that still look fine, and it is inclining me to believe that a well maintained early 1980s or late 1970s watch should be no different that it will outlive you.

Any experiences or stories are very helpful.
Thanks to all