Director of Testing Laboratory

We recently purchased an ICP instrument from thermo-fisher.  My question has to do with the Argon gas supply.  We purchased one of the very large Argon dewers, and it it lasted for only two weeks.  I was told this has to do with the venting of the dewer, and that this short life was expected.  Is it better to buy the smaller cylinders that do not vent?
I was also told that they recommend keeping the instrument in stand-by mode, and thus constantly Argon purged for the sake of the internal optics of the instrument.  Any experience out there?  Need to get this resolved quickly.