I've been stringing 1-2 rackets at a time, then, a month or two later, 1-2 again, off and on for 20 years. The fastest I could comfortably string one was 45 minutes. Last week, I strung 5 rackets, one after the other. The last two took me less than an hour (less than 30 minutes each) and I wasn't rushing. Everything about my technique improved with each racket. This never happened stringing 1-2 rackets a month. I'll be interested to see if the improvements stick when I restring in a month or two.