I grew up riding bmx, so i was always on a smaller feeling bike. When i first started getting into vintage bikes, i didn't give too much though to size. So one of the bikes i have that i absolutely love, is an 82' Schwinn Le Tour Tourist. It's too small for me, 21" i believe. I'm 6'. I've taken it out for a few mini-tour bike camping weekends. One of which i did a 7 mile climb over a pass. I was dying!!! Of course i only had 10 gears so that didn't help.

Fast forward to recent and i picked up a 85' Raleigh Alyeska that's about 23". Night and day as far as fit is concerned. I can climb much better, i'm faster, etc. I still love my Tourist and will still do some light vintage touring on it, but nothing that involves a climb.

I think the hard part about being into vintage bikes is finding them in your size. I think it's definitely more important if you're looking for a vintage road bike or touring bike that you still want to ride heavily vs just having around for looks and collect-ability and just riding short distances.