More than narrow tread tires.
Some say to change your auto tires every 5000 miles. Other people just check the tread on their tires and when the tread looks worn, they switch their tires.
While it is good to use tires with the same tread and sizes, it is possible to use tires with different tread patterns, though you should be careful as the performance of the two tires may be different, causing your car to be unbalanced, endangering your passengers.
If you're having to put air in your tires frequently then your tires probably need replacing. Also if the tread on the tires is worn down they should be replaced (a symptom of worn tread is the tires squealing on the road for no apparent reason).
Minimum tread depth for all 4 tires is 2/32"
In the tread there are small 'bars' at the bottom surface about 2-3 mm high, when average tread wear is down to these 'bars' you should get new tires.
Winter tires should be changed out when the tread has been worn down to around 1.5mm to 1.6mm in thickness, after they have been worn down more they are considered worn out. To measure the tread of ones tires one should use a tire gauge which can be bought at websites such as amazon.
For year round tire care and hazard prevention you should be sure that your tires have at least 1/8 inch of tread.
60% tread wear.
You should replace your vehicles tires approximately every 60,000 miles. Or when the tread on the tire is close to all gone.
On or before your country's legal minimum requirement for tread. If in doubt see out a qualified fitter to check the tread depth for you
Tires should be replaced when the tread wear reaches the level at which your state no longer considers them safe usually 2/32" or when they begin to show signs of irregular tread wear or weather cracking.