I'm finding lots of benefits of endurance training, not just cardiovascular but also kidney function etc.
I don't work out a lot, usually three to four times per week, but the difference in my fitness and ability has changed dramatically over the last year.
I just completed my fourth ultra marathon this weekend, and while it was a hard run (actually, a very hard run) the only limiting factor for me was cramping calves because I went out a bit too hard on the first two big hill climbs.
A year ago I wold never have even dreamed of doing this. But now it is all doable and I'm looking for a bigger challenge.
I started running when I was 52. I had been reasonably active before that, but the longest I had run was probably 5km (and that nearly killed me!).
So if you are thinking about getting into some endurance sport, I'd say go for it. You never know where it might lead you.