How long to look? As long as you like.

Once an object stops being interesting move on. But do try different magnifications including high power for detail.
To get you started grab a guide like e.g. Southern Sky Guide by Ellyard and Tirion comes with mag 6.5 charts (just right to begin with) that cover the entire southern hemisphere. The sky is split into some 15 or so segments and there is a page on each describing (some of) the best objects in the region. Once you've done those you can hunt down the rest of the objects on the charts. This would keep you busy for quite some time (a year and then some).
If you haven't yet, get a good pair of binoculars for hand held stargazing. 7x50 (I'd say 7x42, but that's uncommon), 8x42 or 10x50 depending on how steady you can hold them. 8x42 is shaky enough for me already. Without any charts you can use the binos to look for interesting targets to point your scope at.