im 210ish and have run a couple half's in my time (7 years ago and 15lbs lighter)
i run from beginning fall to end spring here in texas
my standard weekday run is 5.15 miles and my best time is 43 minutes - this morning's run, which was the 3rd of this running season for me, i did in 46 minutes - i plan on getting down to 40 minutes. i ran 7.089miles sunday in 1 hour and 6 minutes - as it was my 2nd run for this season, i was happy with it, but plan on getting it down to an hour.
i find that running is more mental than physical - the body can do it, its just convincing your mind that you have the endurance. same goes with jumping rope - most people burn out because its a rhythm issue, not a speed issue. i jump rope twice per week and do 32 minutes, but could go for an hour if i needed to.