Can you swim 500 yds, bike 17mi, run 3.1 mi with no break? I can't yet, but I will in August.
You betcha, though my time wouldn't impress you. I wouldn't be crippled the next day though.
About the best training advice anyone can ever offer you is this, if you desire to be truly fit, and everyone should, then whatever you suck at, whatever you dread the most, is what you should be doing. If you can't do one box jump on a two-foot box, that should be what is known as a "clue".
Skinny guys can run, skinny guys, some of them anyway, can do pullups like you (and good for you that you can), but skinny guys dread a heavy barbell, and that is what most of them desperately need.
No-necks who can lift pickups, dread running and doing any sort of real metabolic conditioning. Guess what they need to be doing?
I'm not an advocate of bodybuilding per se, but a lot of the old time greats, who didn't over do steroids and take the Lyle Alzedo route, like Frank Zane for example, still look like studs today as old men.
As for endurance athletes and aging, have you seen Marcus Allen lately? He looks like a meth-head.
Don't run another step, for now. Buy and read Mark Rippetoe's "Starting Strength". Find a coach for the lifts. Then find a Crossfit box and join up and do that for a while. Then add in Crossfit Endurance programming to your training. Your time on a sprint-tri will probably be about the same, but you'll be twice as strong and a better person, husband, and parent.
Oh, BTW, endurance athletes incur several cancers at a MUCH higher rate than even non-exercisers, ask Lance about it. There is a reason for that.
