WE never go more than 3 days, because of the fear of lipodystrophy. However, i think the length of time a site can go before it gets occluded with gunk from the immune system is anywhere from 1 to 7 days for different people. Theoretically at least, then, there are people who can use a site for 6 days without a decrease in insulin in the short-term. In the long term though I think they’re still setting themselves up for scar tissue and fat accumulations that will reduce insulin absorption.
Personally I say why risk it unless you have major financial barriers to getting more supplies. In which case I’d just switch to needles.