I've stayed near Lihue, but that's not where the best stuff on the island is.

Both Princeville and Poipu are fantastic places to stay (for different reasons), but if you're going to stay in those places, I would just commit to being there. There's really not anything (short of a helicopter ride) that you should need to head back to Lihue for until it's time to go home.

The only other possible exception I can think of is the Wailua Falls, which is a really cool place to visit. There's also a Smith Family Luau place just north of Lihue, but once you've been to the PCC, there's nothing you'll see or experience there that wouldn't be a letdown by comparison.