
To be honest once you are a real adult with some expereince of life then age gaps are not going to make much of a difference.
My dads wife is 30 years his junior and slightly younger than me.
When they got together she was 19, so I did not really approve for her sake (taking on so much baggage has not been easy as Dad had five kids from 19 down to 7 years old), as he had expereinced so much in life and she hadn't yet really started hers.
My Dads sister married a man 25 years older than her who she had had a relationship with since her divorce when she was in her late 20's.
The only thing is with a large age gap the likelihood of being a youngish widow are increased, and health of the older partner may not be as good as the younger, but doesn't follow.
My dads wife at 42 has more niggling health issues than my Dad at 72.
There is also the older partners family to consider, they may disapprove, and you may find it awkward dealing with his children or other relatives without being a generation removed.
On the other hand I have no problem dealing with my dads wife as a freind, but there have been times where she as my Dads partner has tried to take an upper positon as his wife, and I have just let it go, but with another person might cause resentment.