It's age, and it's normal, but it may not be irreversible. I'm in my mid-40s and can pop twice in an hour and three times in 90 minutes. Here's what I do:
1, Make sure you're comfortable and attracted to the WG. This may sound obvious, but I've tried to force a second round with girls I'm not into and it's a disaster. If I'm relaxed, I can go forever.
2, Don't cum for 2-3 days prior.
3, Do watch lots of porn. Having an erection for an hour or two in the run up seems to help. If possible, I look at porn the day of the meeting.
4, Get in shape. Again, sounds obvious, but it makes a difference. I've found that going to the gym before the meeting helps my energy, too.
5, Avoid stress. Sex may help you blow off steam, but whatever is stressing you out will return after the first round and make the second one harder. I stopped punting midday because I found I was just thinking about work.
Hope that helps.