[dbatten]

7.100 times would be written "7,100 times" in the US. Using a cloth bag 7000 times at one grocery store visit per week is 134 years of bag reuse.

[liability]

Okay I see. (7,000 would actually take about 40 years for me, but I live next to the grocery store and rarely buy fresh food more than a day or two before eating it.) How does the energy needed to produce a grocery bag that will last a lifetime compare to a pair of blue jeans that will be worn out and out of style in five years?

Avoiding plastic bags seems like premature optimization.