question re: shelf life

[Emma09]

Is it a best before date?
A friend of my mum contacted a different formula company who said it's safe for 12 months opened.

[emc2]

I felt that it does go off after a month, just imho.

My SIL brought over a tin that she'd opened a few months earlier for me, and it just smelt "off".

I think it would also be the added nutrients in the formula would not last after that time as well - the vitamins and other things, and just the contamination of opening and closing it.