Well 50 isn't exactly what it used to be, lol. Nor is 30 for that matter!
But regardless of the age, you're into what you're into and if you're into tickling a 50 year old - or a 70 year old for that matter! - so be it, you can't help what you like. The other end of the spectrum is where the danger zone comes in, at least in so far as actually going out and doing it. But if you like tickling a 50-year old, I say go for it. I'm about to turn 51 and there are alot of people my age that I think look fantastic, and I would run my hands over in a heartbeat if I ever got the chance. Julianne Moore, who is older than me, was just tickled in a movie....and I thought it was super hot.
At the end of the day, they're all just souls in a body. I look at pictures of people that I used to think were "old".... and all I can see is how young they look! And often beautiful! When I see older people, I can often see (or imagine) the young person that they were. Most people I know still feel like they're a younger version of themselves inside, anyways. I know I'm very much a guy in my 20s in a lot of ways, even though I'm twice that age. I still feel perpetually 23, lol.
I'm sure there are some 50-year olds that would LOVE getting tickled by someone younger. Go get 'em!
