You can stay as long as you want at Urca Hill or Sugar Loaf Mountain.
Once you get off the cable car at Urca Hill, you can stay there and enjoy the view of Rio de Janeiro as long as you want. The same is true for Sugar Loaf. However, the majority of the tourists visiting Sugar Loaf on their own enjoy the views from the top of the hill for at least 30 minutes. If you want to take your time and have a drink and a snack, one hour to one hour and a half should be sufficient.
At Urca Hill there are many benches to take your time to enjoy the views. At Sugar Loaf, on the other hand, there are much less places to sit. The trick is to go first up to Sugar Loaf, get it done, and then take the cable car back to Urca Hill where you can take your time until you are bored.
To learn how long most visitors stay and how to visit Sugar Loaf in Rio de Janeiro, Brazil, get a copy of Sugar Loaf: the definitive guidebook to visiting the Rio de Janeiro’s most famous hill.
For comprehensive travel information about Rio de Janeiro: My Rio Travel Guide: The Essential How-To Visitor’s Guide to Rio de Janeiro