I only ever did one half-hour, about two and a half years ago. A girl calling herself sexyXXXstunner, long since inactive but a bloody good fuck.
I was in, out, (pun intended) and driving back home and it felt like nothing had happened.
Nowadays, I'm leaning towards less frequent but longer punts. It takes me at least half an hour to pop the first time and then another half hour to reload. I always find something to lick, nibble, tweak or poke my fingers in, during reload, though.
As already stated by others, my money, my time, my punt, my pleasure.