Had the roof redone in 2004 and now I'm loosing the shingles. Had to replace shingles in three different areas of our roof. When I went to recover those that had blown off I descovered they were improperly installed. I also found that the whole roof wasn't done as per the manufacturers recommendations . No felt underlay, incorrect nails, not removing the adhesive strip and the list goes on. Depending who you talk to some say those things shouldn't create an issue. Being a tradesman myself I know why there are certain recommendations made by manufacturers. They may seem time consuming etc. but for a good installation they should be done.
If you're going to get a roof redone do your homework. There are lots of instructional videos are on the internet and manufacturers websites. Watch them and make sure your contractor gives you the right answer when you question them. DO NOT go for the cheapest price. They can't short change you in materials so they'll cut corners elsewhere.
We have an old garage in the back with all its shingles still in tact after 20 years. Why ? Because it was done correctly from the start.
No excuse, Manny! You're a hack...