Firstly I used to work in a car window tint company in Australia. Legal limit there is 35% and Meaning it lets 35% of light through. No front windscreens allowed. Never buy window tint from the dealer as it is marked up excessively. They outsource it usually to another company in Australia. To remove old window tint you steam it off. We also used an ammonia based solution to remove the remnant glues. The rear window demister need to be treated carefully as the bars may come off. So steam and peel slowly works well. A good tint film will be 3M in Thailand or Solargard or Luminar. Cheap ones fade and bubble and change colour quickly. Generally we give a lifetime guarantee in Aust. but it is only for purchaser. Cars are usually flipped in 5 years and the tint usually lasts 10 years. Find out more by checking tint manufacturer websites. https://www.solargard.com/ Does have benefits. https://www.solargard.com/tint-laws/ shows no windscreen below AS1 line of top 5 inches of screen. Regarding UV light Glass already removes UV light. Especially front screens according to this link. Window film removes UVA and glass removes UVB. https://hps.org/publicinformation/ate/q12082.html Cant get sunburnt through glass. The reason for the 35% limit is safety at night. Window tint cools your car. Put 35% all round the side and rear and you should be fine. You can go darker in the back. I had a station wagon and had 5% rear so no could see in there and 20% on the rear sides. In Thailand those front windscreen and dark tints are a danger in unlit areas as night. One good thing about window tints is that if the window breaks the film protects you from broken shattered glass. Hope this helps.