That depends pretty heavily on the area you are in, the type of weather and environment you have and most importantly how the roof was installed.
Most manufactures include a 15 to 30 year limited warranty on traditional asphalt 3 tab shingles, so that is a good place to start.
You can assume that the manufacturer is going to be sure to only warranty their product for the assumed 'best life' of the product, so in a best case scenario I would tag on an extra 10, 15 maybe even 20 years if you live in an area with mild weather.
Most people are not that lucky. In my experience asphalt roofing tends to start showing its age at around 7 to 10 years. In temperate climates with medium humidity you will start to find algal staining. If you roof is near a tall tree you can get damage from debris or dampness. Cracking from excessive heat exposure. 3 tab roofing can also be effected by conditions with in the house which can cause nails to 'pop up' under the shingles compromising the condition of your roof. Weather plays a very big role in the life of your roof. Strong winds, hail, freezing rain, heavy snows and even excessive UV exposure can take decades off of your roofs useful life in just one day.
Other issues that can prematurely age your roof include improper venting, inadequate flashing, non functional gutters or clogged gutters (this is a very big one!!!) Quality and age of the sub roof materials. Quality of materials and installation of valleys, ridges and flashing around chimneys, vent, skylights and other roof components. (These are the first to fail on a bad roof install, and they can ruin a whole roof as well as you home with in when it goes!)
They are usually guaranteed for 30 years. However, they are now making a shingle that is guaranteed for 50 years.
One hot sunny day.
Nope
Depends on the type of roof and type of shingles used.
It really depends on the size of the roof and how long you have to work on it.
Refer to Fastest Shingle Roofer answer
We were looking at shingle samples for our new roof.
My dad had to replace a shingle on our roof after the storm blew it off.
Lots of reasons: they last longer (some say as long as 100 years!). The snow slides off from them much more easily than a shingle roof. They look nicer, and increase resale value.
A shingle...
As Florida roofers, we have inspected thousands of roofs of all ages and materials, and based on our experience this is what we believe: A shingle roof will typically last between 15-20 years before needing replacement. A metal roof system will last 35+ years. A tile roof will last anywhere from 20-40 years before needing replacement.
A leaking roof can be a headache for many owners. In addition, a leaking roof can cause extensive water damage inside a home, potentially damaging the foundation. A shingle roof is simple to repair. Locate the damaged shingle on a rooftop, and pull back the shingles above it. Using a claw hammer, remove the nails holding in the damaged shingle. Check for any existing damage to the tar cover. If there is any damage, repair it with silicone or roofing tar. Place the new shingle under the existing roof shingles, and nail in place. Make sure no other shingles were dislodged.
Composition roof lifeAsphalt shingles are rated at 20, 25, 30, or 35 years. The average roof life is 5 to 10 years less, depending on climate conditions in your area. The life of any asphalt shingle roof is effected if Algae and Mildew is allowed to grow on it. The plant wraps it''s roots around the granules on your asphalt shingle roof, and as it grows, it can actually force the granules to come loose. Proper non pressure roof cleaning will extend the life of any shingle roof with black streaks or mildew growing on it "
The type of shingle you need really is a factor of what slope your existing roof has. A low slope roof needs a much different type shingle than a high slope, as water can intrude under the low slope. In this situation, a different type roof might be a better option.