Not unreasonable under many circumstances...judging by the mental and physical condition of most Americans. That said, if he's physically fit and mentally sound, (not to mention capable with his firearm), then it might warrant reconsideration. I keep myself fit...but I'm not as strong nor do I possess the same cardio I did years ago...and I still have a handful of years before I reach the age you're discussing.
If there's nothing to stop him from carrying in church, I see no major harm done, especially if he can let those on the team know so he doesn't get targeted in an incident.