Starting strength has you do six to eight sets for each exercise^1. And it recommends "[taking] enough time between sets so that you don’t feel any fatigue from the previous set before you start the next one. For guys squatting 185 pounds in their work sets, this is five minutes between sets."^2. If you're doing six sets, and each takes you, say, a minute, and you're waiting a few minutes between sets, that easily adds up to more than 20 minutes per exercise. Also, if working with a partner (which you do dismiss), you're going to have to alternate. Alternating doesn't quite double your time, since you have your rest period while switching weights and doing the set, but it does increase it.
> When you're starting out and learning the form, sure, a partner to check your form is invaluable. But after that, I never felt the need...my body knew when something wasn't quite right.
I've heard a lot of stories about people who thought they knew they were doing the right thing, but badly injured themselves. I mean, I hope you're right, but I doubt I am. Also there's spotting for bench press (people die from benching without spotters or doing so in a cage), and if, for example, you go down for a squat and realize you've got too much weight, helping the weight go down less uncontrollably. Perhaps I could be more comfortable with benching alone if I did so in a cage, but I've never seen anyone else do that. Perhaps I could be more comfortable squatting alone if I got comfortable dropping the weight off my back. But right now I'm not -- so having a partner is helpful.
And finally, I'm also including changing before/after and showering in the two-hour time, since that's something I have to account for in my schedule. Being able to leave the gym 60 minutes after I got there would be pretty nice, actually. Even a little bit more -- 75 minutes -- would be great.
Perhaps I could try it again, having one personal training session a month to ensure my form's ok.
[1] This is from what I recall. Squats were the most -- a set with only the bar, three or four warmup sets, then three working sets. Deadlifts had only one working set, and everything but squats had only three warmup sets. I could be wrong, but not by much.
[2] http://www.muscleandfitness.com/workouts/workout-routines/4-...