I feel like the thicker ‘bags for life’ are a bit of a false economy. I could be remembering wrong but with those, you need to use them something like either 12 or 20 times for them to work out as being less harmful than the old disposable plastic bags.
I try to avoid using them where possible but where I can, but when I have, I can’t say I’ve been able to use them more than 5 or 6 times on average.