Coconut - I don't remember how old you are or what stage of life you are in - that can make a big difference.
Example - if you're young and think you might like to have another kid one day, dating a woman 8 years older is a dumb idea.
On the other hand, if you're 50 and she's a vibrant sexually active 58 - she's still likely to outlive you.
Longevity runs in my family (mom is 87 and just retired last year, her mother lived to be 99).
I think that this is actually a smaller age gap than the other way around - that is, a guy 8 years older than I am is likely to die 10-20 years earlier than me, whereas a guy 10 years younger might last as long as me.
I DO think though that some men's egos can't handle dating a woman who is older - because some men are used to being the "older, wiser. more powerful" person. My ex-husband was 4 years younger than I (we married when I was 30 and he was 26, which was a bit of a gap) and I think on some level it always rankled him, especially as I was his professional equal and he knew that I did better than him on exams in school (which I never felt was significant - his type of intelligence is different than mine but equally valid - but it bothered him). When he left he ended up marrying a girl 19 years younger who acts like she's 15 and is not quite his equal in terms of professional accomplishment (although she is a professional). I think she's fine but that there's a part of him that enjoys NOT being in an equal relationship.
For the record, since my divorce in my early 50's, I've dated one man who was a couple of years older. All the others just happened to be younger - ranging from 9 years (Mr Big Lots) to 7 years (crazy ex-BF) to 3 years (CMM). In none of those relationships was my age a factor in any way. The only times it was a factor was a couple of dates who were waaaay to young for me.(More than 15 years). Still friends with them though.
