Good point about landfills, they serve as carbon sinks when plastics make it there.

173 is less than 4 years if you shop groceries once a week or so, I already used mine longer than that (aside from a couple that I lost). Never washed them either. They can last another 10 years I think, unless they are lost.

Those bags are bad idea for random shopping, but they work well enough for regular trips. Just keep them in the car.

I expect people waste more cotton on socks and t-shirts, but that's neither here not there.