I take excellent care of my discs and my GF's 7893 still won't read them in hot weather ... You have to wait for it to cool down before it will work ... So, when you park, you either park in the shade or forgo music for 20-30 minutes after you get back in the car ...
I haven't had a single problem with my 7873 in the past 3 years, though (other than that speaker wire short in the doors, but that's hardly because of the head unit //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif )