Do all old trucks leak or is there an acceptable amount?

[IT Cowboy]

I might catch hell for this post or topic phrasing but when I was looking for a truck a few people told me these old trucks all leak. I kind of thought it was just then trying to justify their trucks leaking but now IDK?

The mechanic I had look at my truck said there are a few small leaks, the valve cover, a small area by the trans and the main seal. He said he isn't a big fan of chasing small leaks on older vehicles and just keep an eye out and keep em filled.

Any leak mitigation experts here, can these trucks be fixed 100 percent and what am I looking at in trying to do so. Are there thicker modern gaskets that will work better, is it worth the effort. Is there any reason these should keep leaking after proper repair?

I could easily tackle the valve cover myself and I have read about the main seal and that it can be done by removing the pan.