I have read various articles that say that 3 minutes is the maximum and that after that your muscles begin to cool down.
That being said, I think that it depends on your workout. If you are mostly looking to build mass and get stronger, then you want to allow your muscles to rest as much as possible so that you can get better lifts each time. If I am going heavy I usually wait 2-3 minutes between lifts. If fat burn and a high heart rate is your goal then rest less between each set. I wait 30 seconds to a minute between sets on these days.
2001 Mustang Bullitt GT #5111 367.6rwhp/378.4rwtq
2004 Black Lightning #789 STOCK: 363.1rwhp/444.8rwtq