The main thing when doing a large piece is keeping it flat in all areas.
I use BriteMax polish to replenish the shine (works awesome for that!) and it leaves a layer of protective film over it. Not sure how much it does or how long it lasts, but that's the claim. onebad95 here (on the 94-95 forums) is a distributor of that stuff, if you want any. Sometimes when I have a tough piece to polish out, I'll use that stuff and it'll help very nicely.
Other than that, nothing. I've heard stories about Zoop where nearly everyone has to redo it after a while, and I am NOT taking half my engine apart to strip and seal again every 1-2 years.
I've used aerosol clears and they just yellowed and looked like crap. Never again.
One thing i've come to realize and I know some others here have as well, is that the better polish job you do to begin with, the longer it stays looking great. Not really sure why, but that's how it seems to go
So, do 'em real well and pick up a known, good compound or liquid polish to freshen it up when needed (wenol, britemax, mothers billet, meguiars nxt, nevrdull, the nevrdull-like stuff that is pink like cotton candy, etc.).
I rarely touch mine, just clean dust off after driving to a show or sitting all winter. That's it.
Just did my friend's + aftercooler 
you're well past addiction and possibly crossed over into obsession.
