I have a list of "athletic bucket accomplishments" I've always wanted to check off:
Sub 3 hour marathon
Sub 1:20 1/2 marathon
Sub hour 10 miler
Sub 35 10k
Sub 17 5k
Sub minute 100yd swim
Sub 30 second 50 yd swim
Sub 2 hour Olympic Triathlon
Sub 10 hour Ironman
Sub 4 1/2 hour 1/2 Ironman
Sub minute 400 meter run
Sub 5 minute mile
Sub 10 hour 50 mile (originally 15 hour)
Sub 24 hour 100 mile (originally 36 hours)
I dabbled a bit in triathlon in my mid to late 30s and then returned to just running at 40. On your list I managed the sub-minute 100 yd swim, sub-30 50yd (and 50meter) swim; a close 2:03 Olympic distance Tri; sub-minute 400 (0:51s in college, and sub-1:00 at age 49). I made a serious effort to go sub-5:00 starting at 40 and never went better than 5:03, although my training was also limited by two kids and a 55hr/wk law practice (and not as talented as Ca$hclay). I am a couple of decades past 50 now.
We each have our individual point at which the ability to recover from high intensity workouts starts to noticeably increase. For me it was age 47. The ability to train intensely and avoid injury gets exponentially harder at some point in your mid to late 40s. If you can't run 5:25 or faster right now, your odds of getting to sub-5 are small. I could still run sub-5:40 in workout at age 60, but couldn't race under 5:20. Those extra seconds get very difficult after 50. It's just a different world post-50, post-60 and post-70. The passing years are a relentless adversary, and you need to appreciate looking for your personal best fitness with the advancing years. Look at the age group top 10 times for the events that interest you and set your goals in relation to the talented guys in your age bracket.