EGTA solution storage - (Jun/06/2009 )

What's the storage condition of 0.5M EGTA stock solution? Do I need to keep it at 4 or -20?
and does long term storage at room temperature be bad to the solution?
I'm suspecting my EGTA stock gets some problem...

I've kept it on the table top for long periods of time without problems.
Look at the MSDS that came with it. It should give the stability in each storage temp.