I have started using a rubber mallet more than I do a torch only because I feel the need the show the guys it can be done without torching the pipe... a lot of them WAY overheat
Like someone (HAZE?) said its a learned process that saves time and labor...
If you heat a piece of 1 inch for 8 secs in the middle of a 90 F temp day your going to have a problem with that connection...Up here in New England when I heat my pipe (3/4-2") it depends on the season...
Mind you it also depends on how your torch head throws heat...The torch head can be set to flame differently... I prefer a fat flame in the summer and a narrow flame in the winter.
Spring/Winter I'll give it a 4 second count 3 inside and 1 on the outside lip for 1 inch.....
In the summer its usually a quick one and a half second inside and one and a half outside...Sometimes less on the real hot days...
With drip its about 2 seconds tops from about 4-6 inches away with a benzomatic propane torch in cold temps...One time I had no choice but to use map gas on drip....Now that was tricky, and involved some skill.
Since my first week of irrigation 3+ years ago I have never overheated the pipe....
lol sorry to blog fellas....
Heating wisely will cause less stress on your body,result in quicker install for a fitting,and if done properly will never compromise the integrity of your pipe!!!!!!!!!!