I do the park and fly all the time in Miami but they have them all over the country. I pay about $7 a day and they wash your car for free after 3 days. It's not too good to be true, it is true. I love it. They have a bus that picks you up right at your car. You don't have to go to a bus stop with your luggage in tow. It's really convenient. They also drop you off right at our car on the way back and help you with your luggage. For me it's cheaper on short trips than paying for a cab. On longer trips then I just take a cab.
LOL - In Boston you pay twice that and then some . . after 3 days you pray that your car will still be there when you return and you hardly care whether it is dirty or clean
Of course if you cough up more $$$, they will gladly detail it for you.
As it is outdoor parking, in winter Thrifty will clear off all snow and ice and have it warmed up when you finally get back in. Having said that, they are predicting a high temp of 67 Degrees F today, March 8th!!! I've not been snowshoeing once all year!!!