20-30 minutes for 1/2 acre lots...

There are a thousand different factors out there that can effect mow time. My mower may be bigger, faster, etc. I don't stop, as soon as my feet hit the ground, I am off to the races. No time for little breaks here and there. When I trim, I am almost jogging with the trimmer. It still looks as good (or better) than the old man next door that literally crawls when he trims. Learn what climb cutting with the trimmer is and when you should and shouldn't do it. Getting used to your equipment is a huge time saver. Finding little ways to save a minute here or there is the only way to get more efficient.
Don't ask me why I am telling you guys this, just to let you try and under bid me next spring. You will figure it out, it just takes a little time and patience.