It's a gas

Hey guys, got a probable "no-brainer" question for you, but my brain is on 
holiday. I have a couple of tall bottles of 85/10 gas on my Lincoln
PowerMig 
that I haven't used for a couple of years while I was busy doing other 
things (driving a big truck for the last year). I'm getting ready to start

welding again, but... is the gas still good? I've heard rumors that the 
argon settles out of the CO2, or vice-versa, but don't know if this is
true. 
Can I just fire up the wire feeder and pick up where I left off, do I have

to "mix" the gas by rolling the bottles on the floor (according to rumor),

or do I need new gas?

Thanks in advance
-- 
karin