Treadmill Etiquette

Whenever I go to the gym, the treadmills are always set to allow you 60 minutes followed by a 2 (sometimes 3) minute cool down. The time of day that I usually go to the gym is pretty good because there are always free treadmills and I've never seen a wait but I still get off after that hour is up. My question: can I turn it right back on and run more? I really want to keep my mileage up but can only go so far in 60 minutes, obviously. If there is no line, is it still rude to turn that puppy back on? I'm a crazy obsessed rule follower and am convinced that the gym-police are going to come after me if I keep going. Oh, and the gym I go to does not have any sign posted such as ones I've seen that say "There is a 30 minute limit on all cardio equipment"...I saw one like that at a different gym I went to yesterday. That one got to me too because there was no one waiting. Sigh. I obviously need advice because the last thing I want to be is 'that rude woman' at the gym!