We have a Calais V too. It had Michelin Pilot Sport 4s on it when we bought it (245/35/ZR20s), with approx 5,000 km on them. We got around 30,000 km in total from them, so 35,000 km in total - pretty much commuting driving. They probably still had a few thousand km on them when we changed them recently - one of them is now our full sized spare, with plenty enough tread left on it to be still legal. We didn't experience them losing any chunks of tread, but they did wear out their sidewalls far faster than the overall tread - and that was with good alignment and tyre rotations.
I wasn't looking forward to the replacement cost for the Michelins though - around $520 each - so we went with Bridgestone Potenza Sports during the buy three, get one free "deal". $439 each, but one was free. Around $1,400 for four tyres fitted, 4 wheel alignment and swapping the spare tyre to the rim with a bit of gutter rash on it. It's always difficult to gauge the performance of old tyres vs brand new ones, but so far, I think the Bridgestones are holding up well compared to the Michelin Pilot 4s. So far, same grip, same feel, less noisy.
Oh, and if anyone is Adelaide based, we got them through Bridgestone at Golden Grove. Very good service, they respect and take care of your car, and easy to deal with. We have a number of cars, and we go there for tyres for all of them.
