Barring accidents or diseases brought on by stupid behavior (excessive drinking etc) my family on both sides is extrememly long lived. My dad is 78 or so and still in perfect health. Walks 5 miles a day and then walks the golf course or goes bowling. Strong as a horse. My mom's maternal Grandma and my dad's maternal grandma both lived into their hundreds, both in good health all the way. (In fact cataracts killed my dad's grandma. She was as solid as a brick house and loved to do needlework. When she lost her eyes she lost her will to live and died within a year.) Rest of family, mom, aunts uncles etc, all doing well also.
I am in pretty good shape and getting in better shape every day (walk a lot, drink a lot of water, losing weight (I'm down 17, only 23 more to go) work out daily). With proper diet and exercise, and proper attention to one's health and lifestyle there's no reason someone shouldn't be able to live well into their 90's.
But beside all that, If the lady wants to marry someone older who she loves why stand in her way? Age discrimination. "Sorry ma'am but you can't marry someone more than ten years older than you"
Also there are no promises. I married a wonderful woman who was 5 years younger than me. Now she's in heaven and I'm a widower. Age doesn't make a difference in God's plan.
Seeking out someone specifically much younger than yourself has downsides for the younger, and we described those above (and we've talked about them before)
Some seek out the age differential for very selfish reasons. In those cases, it's creepy.
I understand your motives (now) John, and wish you well. I really do. :~D
You can kid yourself that it's okay because your are proceeding to find her using a method devised by religious people, church women are helping you look and because your intentions are to have children.
You are 45. To plan on a large family at this age is unreasonable and unrealistic. If you were looking for someone of 35 and were planning a few more children that would be far more realistic, and far fairer to the woman. But you aren't considering the woman's needs only your own. Therefore, while I would love to be able to wish you well in your pursuit, I cannot.