I tend to go for an hour or occasionally longer - 90mins/2hours.....I even did 3 hours with Dee because it is such good VFM and she is so easy to be with, and so easy on the eye.
I have had a couple of 45min punts, but 30mins would just be too short for me......
I am a one pop only guy, so I prefer a natural flow to proceedings and would feel a time pressure to cum if it was just 30mins......on average I guess I am ready to unload around the 45/50 min mark.
If I am on a 90/120min punt, it's usually cos I want to be edged and teased and played with or I have two ladies to play with.......(Ah, wistfully remembers Lucy2015/NSS - SW section, March.......)