Dude, I think that's great! Hell, I'm almost 10 years younger and still have the OEM hips and knees. I would be pretty happy with that 5k time. As far as transition time, you're flying compared to me. If I'm wearing a wetsuit, I'm lucky to get out of T1 in under 10 minutes, around 3-4 minutes if I just swim in a trisuit. And T2 is generally 2-3 minutes for me.