Meh. Every person gets to make their own decisions. Frankly, it is rare in today's society for a relationship to last a really long time, regardless of age. There are plenty of couples who are close to the same age whose relationship is unhealthy.

Personally, I am 20 years old right now and wouldn't date a 45 year-old. Not because I feel I am too immature in comparison, but because we would be at two completely different places in our lives.

Worst case scenario - the two individuals try a relationship, and it doesn't work out. Doesn't sound so different from how a lot of relationships end up.