I have definitely gotten back with a former partner after years had passed...I met my ex-bf when I was 19, kinda like you OP. We went out for 4 years and then broke up over some stuff related to our age difference (he was 12 years older). We still liked each other though, there weren't really hard feelings...we both travelled separately and lived outside our home city for awhile, but we crossed paths again 6 yrs after we had broken up. It was really great, but eventually we started to have the same fights we had when we were dating before, and it didn't work out too well...we broke up again, and while we have hooked up occasionally over the last 2 years, that's as far as it goes.
I tend to think people usually break up for a reason. There are exceptions of course, but generally it's hard to overcome past issues when you get together with an old lover...best to enjoy it for what it is.