Had my first (now 9-year-old) child at 39, my second (8-month-old) child at 48. Yes, with the same (1st) wife (we're celebrating our 10th wedding anniversary tomorrow.)
1/3/5-a.m. feedings have never been a problem with me, as Nature didn't equip me with the ability to lactate (sorry for any unpleasant mental images that might conjure up) and hence I can sleep through till 6 a.m., at which time I have to wake up and get ready to go to the office.
Changing diapers hasn't really been a problem since my wife is East European and they have a knack for toilet-training babies very early (no mess, no tears.)
Teething is a minor nuisance.
Holding my 8-mo.-old boy up to my face and looking into his eyes is more than enough compensation for any of the difficulties associated with raising him. Other middle-aged men go mountain-climbing, run marathons, or engage is other high-risk pastimes, which activities are at least as exhausting as carrying a 9-kg child in a harness on your chest during an all-day downtown shopping spree. Jedem das Seine. (To each, his own.)
Am looking forward to having another in a few years.
However, I admit that I have not yet gathered any experience with pubescent children (vulgo: "teenagers.")
Regards,