Ring Road

It all depends on how much of the country you actually want to experience. Some people just drive it without seeing anything except through the windshield, and other people take weeks. Based on my experience, I would not do this with less than 10 days, and that would still be rushed. We have been many times, but only done the ring road once, so far. We had 12 nights for that and still missed so much, thus many return trips. We head back again in May for 14 nights, and IMO, that is an optimal time for the ring road.

All that said, that is if it is summer and weather cooperates. If you are talking from September through May, you could encounter some rougher weather and of course shorter days.

Give us something more to go on and we can give better advice:)