I think it depends on the individuals involved as to whether a relationship can last. Although I do think that age can play into it because of experience bias that everyone gains through life in general.
While I was in college, I had a purely physical relationship with a much older woman named Diane. I was 21, and she was 47. She was actually 5 years older than my own mother. I met her at a club in Seattle. I knew then that she was older, but not exactly by how much; but she was as hot as Hell. She had been married to a guy who owned one of the largest limo companies on the West coast, and was his trophy wife. He was out chasing younger women, and neglecting her, and she'd finally had enough- divorcing him, and taking him for almost everything.
She lived in a huge house with her daughter who was a year older than I was, in the very prominent neighborhood of Medina. We wound up in a hotel the first night, and then stayed there the whole weekend. When I left on Monday, she told me she didn't care if I was seeing anyone, she would like to keep having sex with me. During my college years, I played football, and took full advantage of all of the sex I possibly could get. So, I was totally into it.
Diane started buying me stuff. Lots of stuff. Watches, suits, work out clothes, etc. We started going to the nicest restaurants; concerts, plays, ballet. We had sex a couple of days each week. My roommates, Martin and Karl, and I used to hang at her house and swim in the pool all of the time. And if she called me and I was otherwise occupied, she was totally cool with it all. She didn't care who I slept with. In fact, she got into it. She'd ask me to reenact things I did with other women. And she taught me a lot sexually, and she was insatiable.
This went on for about 9 months, and during this time, she kept telling her daughter, Letty, that I was just a friend. I saw Letty so much that she and I started to take an interest in each other, and Diane knew this. At one point, she asked me to seduce her daughter and show her what great sex was like. Over the next few months Letty and I hooked up a few times, and one night afterwards, she told me, "My mom said you were great, but I had no idea just how much."
The next day, I was really just weirded out by the whole thing. My old roommate Martin, to this day, thinks I'm crazy as fuck, but I couldn't do it anymore. The gifts, sleeping with her and then her daughter, with both of them knowing and comparing notes- it was too weird, even for me!
I broke it off with Diane and actually dated Letty for a few more months, but her mom started getting jealous, and I was just wanting to hook up with lots of different women, so I ended that too.
When I was 35, I met a young model at a bar that I frequented. She was 26. It started on a purely sexual basis. We couldn't keep our hands (and other parts of our bodies) off of each other. We started dating and three months into it, we discussed her moving in with me. We were having a great time, and the sex was incredible for both of us. About two weeks after she moved in, I came home and she was in tears. Naturally, I tried to comfort her, and wanted to know what was wrong. She only cried harder and told me she loved me so much and didn't want to lose me. So, I asked, "What's this all about?" She told me that she wasn't 26, she was only 19! Then it all came into laser focus-outside of the bedroom we didn't really have much in common; and I swear to God, my brain immediately went to "Hey Nineteen", by Steely Dan.
We had great sex, but we had nothing really else in common. She got very few of my references, and slowly it started to really frustrate me, because outside of the bedroom, her inexperence about 'life" was naturally profound. It was especially awkward when our social circles tried to hang out as well. About six months later, I asked her to move out.
I have friends who have made huge age differences work. One good friend is 14 years younger than his wife. Mrs. Vox is 8 years younger than me. There are times, of course she doesn't get a reference from my youth, but not too often.
But I think it can be a big deal for some people.
EDIT: I just reread my post, and realize I could have started it out with... "Dear Penthouse Forum".
Wasn't intentional.