"Middle youth" was a term in fashion some time ago to refer, with suitable discretion, to those reaching a certain age.
Middle youth is when
..... a health care professional is complemented by one of her clients because, for the client, she looks like her grandmother ....
..... the builder comments to her about a tradesman who had quoted something like twice as much for the work that he was doing along the lines of "Oh, when they see a little old lady .."
.................. and the October half-term holiday is abandoned in favour of Zero booking in to a health spa for a a long weekend.