L.P.
My son has also been potty trained for almost 2 years now (he's 4 1/2.) But he still has occasional - not frequent, but occasional - nighttime wetting, regardless of how much fluid we limit, and regardless of whether he pees before he goes to sleep. And I REFUSE to wake him to pee once he's asleep. He's never been a good sleeper, and often when fully awakened, he will have a horrendous time getting back to sleep.
SOOO, we use pull-ups. Like you said, we'll re-use them for a couple days if he's dry. But the other thing I've considered is layering his bedding. They make waterproof mattress pads - not the fitted sheet type - but a protector you simply lay under the sheet. I've considered putting on a sheet, then the protector, then another sheet. That way, if he pees, we change his undies, pull off the wet sheets, and he should have a dry sheet underneath to sleep on.
Personally, I don't really like the option of using the plastic covers over his underwear. I think that would be really uncomfortable on a bigger child.
They also make cloth diapers out of a fleece material - getting quite popular - perhaps they make a pull-up type for bigger kids? Just thinking out loud here, well not really since I'm typing - LOL - but I am going to look into this myself. Would save a lot of money in the long run. If I find anything, I'll post it.