I've spanked women as old as their 80's, including one extremely kinky woman I'd been disciplining for many years. I currently have a few in their 60's and 70's, and I still like a good spanking myself once in a while.
I think some older people may have a difficult time accepting a spanking from a person who is significantly younger, but it doesn't need to be that way. When I was a lot younger I was often spanking women who were 20+ years older than myself. The important thing is to be able to make a solid emotional connection with both of you on the same page about what is being given consent for, and what the wants and needs of both people are.