I think life can be very complicated at times because this is a touchy subject. Again what makes life so amazing is that on each topic we all see things differen to one another and really its no different to how I just said it.
First let me say I dont see age different as a big problem but then its something that being in anyone elses shoes differs because :
1 - Being a man of maybe in your 20's and 30's and wanting a relationship with women above 40.
This can have more con's than pro's and one of the biggest con' is the "CHILD TOPIC". I he wants children or more children and she cant give him any....almost sure he will go outside the relationship and make them.
When she might not have the urge for sex sometimes and he might have because seeing that he is younger and maybe wants to prove himself and sometimes she might be exhausted....you can be almost sure that he tends to look for satisfaction outside (especially if he is not someone with patience and an open mind).
Sorry to say this guys but some men also are not yet matured and a women way much older than you might see things differently and there is where the miscommunication might start.
2 - More often relationships between women 30's and older men can work out to an extent.
Men can still make children at an older age and as long as the two in question can see with each other and they settle for each other. A woman in her 30's can make kids and this is and wont be an issue whereas women in their 20's you wont find that often with men in their mid 40's and 50's.
Not being of finding themself being old the younger women will want to go out, have a nice time and not always will the older men see themself doing this and one really big problem you can have here is that she might find he is not willing or he might eventually accuse her of mixing with someone at the club and blah blah blah...
This is a really complex situation and what I just summed up here are just a few...there are alot more to having a relationship with someone much younger or older than you....as I said ....It differs from situations.....