I didnt bother reading the warranty as it only cost $70 and the tint on its own is usually pretty cheap anyways [parts]. I am sure the bulk of the $70 would have been labour...I am just guessing though!
The Premier guys have been around a while too [not that i personally think it matters too much] I believe. They also do skylines all the time...also cars a lot more expensive than ours...I am talking cars over $100,000+ porsche, ferrari, etc.
As long as you are happy with what you get [including price] then nothing else really matters!