Depends on the plug and the lube. With a comfortable plug (rounded edges, long neck, nice base) I can go a long time. What do I like to do with it in? Many things - best is if you're moving around so the plug moves, sitting down is also good if the base can bump against the chair and move the plug. Need I add that sexual activities are also fun?
I generally do stay around my house. I have tried wearing one out, but if I'm at my place then there's a better "escape route" if I need it.