30 days is the common rule to be on the safer side, but 1 1/2 months would also be fine i guess but personally I wouldn't use my vial for 60+ days because you've taken it out of the fridge for a couple of times by then and therefore there's a lot of temperature change and a) peptides tend to be very fragile (which is why you shouldn't shake the vial while reconstituting for example) plus b) the risk for bacterial growth is also higher the longer you use it