Make sure that the grommet was installed with lots of silglyde cream applied. If not, it may not seat properly and will degrade faster. Same goes for the o ring. No RTV or anything else but silglyde rubber lubricant on the o rings & grommets. Also, make sure the rim surfaces for both the o ring and grommet are spotless. The grommet must be torqued per the TM. I think I recall 60 ftlbs, but don't quote me on that. Anything less will leak after mounting.
Harbor Freight has a cheap but very effective 2 ton engine hoist that folds up. That, a 3/4 air impact, a breaker bar with obligatory 6 foot pipe cheater and a gallon of tire mount lube makes the process of dismount and mount a reasonable 1 man job. New tires, grommets and o rings = no leaks on my A3.
Here's the link to the procedure and all the details on how to treat the parts:
http://www.steelsoldiers.com/deuce/73238-a3-tire-change-procedure-1.html. It's post #5 on the page.