Using a cloth back seven times is trivial! I've been using mine for seven years. I expect it will last the rest of my life and if my children aren't ungrateful shits this bag will be their inheritance.
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.