Volvie, I suggest you start with some maintenance of your slow leek. Submerse, or soak the tire in soapy water and find the leak. Is it from the past flat, the rim or somewhere else? It's not from the surface cracks.
It seems I didn't explain my concerns as well as I could have-- I was more concerned about the appearance of the cracks in the sidewall as a sign of tire failure rather than as the source of the slow leak.
In any case, thank you for taking the time to respond!
Hopefully your advice will help others who read this as well.
Thanks for following-up! It is really appreciated!
I've already experienced two tire failures (on two different cars/different tire brands) with tires that had no visible signs of failure, so I wasn't going to take any chances-- I went to my favorite local indy, had a tire discussion, and bought four new tires yesterday.
Luckily, they had a set of Michelins in stock in my size and they even had them on sale, so I was able to "save" a little bit of money too. I ended up getting some Ultra High Performance All-Season tires anyway: Michelin Pilot Sport A/S Plus. They seem to be getting some good early reviews, and I like them so far.
The ride is a lot quieter and they feel more responsive than the old ones, which is a definite plus. There is also some rubbing with a tight u-turn, but it didn't sound the same as with the old tires, so I'm not yet sure if one is better than the other in this area...
Visually, they are noticeably taller that the Pirelli P6s and make the 17" wheels seem bigger than they did with the old tires and make the car look a little closer to a XC than it did previously. I like to call the wagon the "elegant workhorse," but I may have to find a new nickname as these tires make it look a little less elegant and a little more aggressive.
In case anyone else is considering these tires, I'll take some pictures tomorrow so you can see the difference.