10 Years' Difference
Going on five years married to my second husband, who is 10 years older than I am. To me, that doesn't seem like many.
My first husband was 15 years older. Age did matter in the end -- it wasn't so bad when we were married at 25 and 40 but at 35 and 50 (when our 10-year marraige ended) the difference seemed huge.
My mother's first husband (my dad) was 15 years older and he always went on and on about it. They divorced after about 18 years of marriage and my mother remarried a man a few years later who is about 22 years older! He's now about 92 and she's 70. And again, here it makes a difference because he is in a home with dementia and many other health problems and she is in fair health.