No issues on mine (2012 335i). The installer did a great job and didn't mention or have any issues. The tint was installed in August, so it's been about 5 months. I got a lifetime warranty and installed for around $200.
I think you may be getting fed some BS so they can charge more. Perks of going to a reputable shop in a smallish market, get good work done at a fair price. As a reference, for the same tint done in the 'city' was at least double. Guess their installers are twice as good...