We like to get maximum use out of everything we buy, but (cast iron frying pans aside) everything has its limit.
I remember a point in my life when I realized this: We were still young and struggling, and we had our first child. Dedicated to the idea of saving aggressively, we didn't spend much on clothing. This was sensible: Clothing is one of those purchases that can usually be put off 'til tomorrow. After several years of doing this, it was time for me to go back to school in the fall, and as I looked at the clothes I hadn't worn all summer, I realized that every item of professional clothing I owned was a rag. Everything was faded, pill-y, stretched, mended ... and in a professional job, that won't do. And my husband's wardrobe was just as bad. Like most people here, I don't feel the need to maintain a fancy or expensive wardrobe, but I do know that it's important to present a good image in the workplace. The upshot was that I ended up NEEDING to buy a bunch of clothes that fall ... and when you wait 'til you NEED things, you give up the choice of collecting them gradually at sale prices.
Determined not to fall into that situation again, I developed a clothing rotation. For example, I 'm doing my husband's shirts right: He wears only LL Bean, which are incredible quality, and they go on sale after Christmas. Every year I buy him TWO ... and he discards the two oldest shirts in his closet. Depending upon his needs, I buy him 1-2 pair of new pants around Father's Day every year (always good sales). For myself, I tend to buy two outfits every spring and two outfits every fall (not always new, mind you). I stand up all day and need to wear quality shoes; I evaluate my shoes at the end of each school year, and if I find that my black boots are too worn to see another season, I have the whole summer to pick up another pair on sale (or through ebay). The result is that we always have SOMETHING relatively new that can be worn for a big-deal day work ... and we always have something that's kind of hanging on for another season and can be worn on a day that we expect to move boxes.
We have a car system too: We have money direct deposited into a car fund so that when our current car dies (probably not for more than a decade), we'll be ready to replace it.
Small things -- tools, cell phones, household goods -- we tend to "hold off on" 'til birthdays or Christmas.