How often should tires be changed?

I drive a lot, at least 20,000 miles a year. I have a cummute and my family lives out of town. I know that's a lot of wear and tear. How often should I change my tires? I don't want to wait until the bust in the middle of a freeway!How often should tires be changed?
The rule of thumb for tire replacement is 5 years after the manufacturing date (The last 4 numbers after the ';DOT'; on the sidewall, with the first 2 digits being the week in the year, and the last two being the year), or when the top of Washington's head on a quarter no longer disappears into any tread groove, whichever comes first. (The old ';penny test'; has been shown to leave too little tread for safety.)



Tires deteriorate with age regardless of mileage, so old tires get progressively less reliable as they age.



Do not wait for the ';wear bars'; to appear between tread segments. At that level of wear, the tire can no longer evacuate water from under the tread, and the tire may aquaplane in the rain, causing you to lose traction and control.How often should tires be changed?
Rotate your tires about every 6000 miles or every other oil change (if you change your oil at 3000 miles).
Most tires have a wear indicator on them within the tread pattern.



You can check your own tread depth with an inexpensive gauge or by using a Lincoln head penny. Slip the Lincoln penny (with Lincoln's head upside-down) into several tread grooves. If you can see the top of Lincoln's head in 2 adjacent grooves, the tire has less than 1/16 inch (1.5mm) tread left and should be replaced. You can measure snow tires in the same manner by using the ';tails'' side of the Lincoln penny. If you can see the top of the Lincoln memorial, it's time to replace the snow tire(s).
well its up to you when you get new ones but the standard is when the tread gets to 2/32s that when tire makers say yo need new ones i never used the penny test but if you take a penny and turn it upside down and the space between his head and the top of the coin is 2/32s