outdated C-41 developer kits in powder form

[TheFlyingCamera]

Ok - I know, the obvious answer is "just use one and find out", but I'm wondering if anyone would have a baseline idea of how long these kits would keep in powder form - I have two old Jobo C-41 Press kits with all the chemistry in sealed foil packets, but these are more than a couple years past their expiry dates.

 

[Sirius Glass]

My limited lack of experience tells me that if they do not show signs of opening and if they have not been kept in the trunk of a car for those years, they are highly likely to be ok. I have used Unicolor C-41 one liter kits several years after the expiration date without any problems.