People often end up paying more for tires than they need to for one simple reason: They wait until they're in desperate need of tires before they begin shopping for them.
Just as people in a hurry to buy a new car because their old one conked out unexpectedly often make a hasty (and costly) purchase, so it is with buying tires when the primary object is to get it done -- not necessarily get the best deal.
The good news is that tires wear gradually -- so the only real excuse for being in a hurry to buy new ones is an unanticipated emergency, such as a severe puncture or sidewall damage that renders a tire beyond repair.
Emergency situations aside, it's easy to anticipate the need to replace tires months before it becomes necessary to do so for safety's sake. Provided one takes the time to do a period check of their physical condition.
A tire is considered worn beyond safe limits when one or more of the grooves in the tread reaches 2/32 of an inch deep. Most modern radial tires have "wear markers" -- horizontal strips that become visually apparent as the tread wears down to the 2/32 of an inch mark. You can also measure tread depth with a tread-depth gauge -- or simply take a penny and insert it in each groove, with Lincoln's head facing down. If you can see the top of Abe's head in any of the grooves, the tire should be replaced. (Any bulges in the sidewall, rips or tears are cause for immediate replacement. Avoid driving the vehicle, if possible -- and if you must drive it, keep your speed down. Sidewall bulges and other signs of major deterioration/damage could foretell an imminent -- and sudden -- catastrophic failure of the tire.)
By checking the tires' condition every 4-6 months or so, you'll know well in advance when it's time to begin shopping for new ones. And that will give you plenty of time to check with local merchants and take advantage of sales -- including online sales offered by retailers who may be able to significantly undercut the costs of a local "storefront" merchant.
The key point is you're not desperate to get the tires "today" -- so it doesn't matter if the sale isn't effective until the end of the month, or if it takes a week or so for the tires to be shipped to you and then a another couple of days to take them to a shop for mounting.
It's also ok to buy replacement tires a couple of months before you need them, so long as they are stored properly (see the manufacturer's recommendations or ask the tire seller about this).
