How many miles on your Jetta? Ever done anything to the suspension? Do you rotate your tires? Do you get them rebalanced occasionally?
The usual suspect in poor tire wear on older cars is the suspension. It wears out so gradually, that after 80 or 100k miles we think it always felt like that and there is nothing wrong. But fact is, your original shocks probably started leaking somewhere between 50 and 75k miles. The struts last longer, but still will be gone by 80 or 90k.
It's a testament to the VW that you can be driving around essentially on springs with very little damping and yet the car still corners great. However, without damping, your tires are skipping across the ground rather than making smooth constant contact.
Steering components also can start to wear and add more "wiggle" to the front tires' traction. Ball joints, tie rod ends, control arm bushings all can get a little loose, and loose means that the tire is gonna wash a little on the road surface.
I'd say it's time to spend some cash and treat yourself to a new suspension. Danix is selling a full set of A3 Bilstein TC shocks and struts for A3's for $200 plus shipping. Find somebody to install them with some new strut and shock mounts and you'll be good. Oh, and while they're at it and will need to do an alignment, have 'em install new ball joints and possibly outer tie rod ends. You'll spend $500 overall and feel like you're driving a brand new car.
The rest about rotation and occasional rebalancing is just common sense for taking care of any tires. Just about every place you go these days for tires offers lifetime rotation and balancing. You just need to add that to your schedule every 10k or so.
Sidenote on the tires, I myself have never been a fan of Goodyears, they wear too fast and perform too poorly for the premium price that they charge. I can't give you a specific long mileage preference because I've never owned a tire I've been blown away by, I just know that I've been very unimpressed with Goodyear.