[brandileigh]

I know that grignard reagents can be stored for some
period of
time, but what, if any, pathways have been identified by which Grignard
reagents are destroyed over time?  Exposure to air is an obvious one,
but
can they react with themselves or otherwise degrade in the absence of
outside factors.

[Mitch]

They are simply not stable species for the most part. And should be used as soon as they are formed for best results. I do not know the decay pathway it depends on what's present.

[bronzezt]

As I know Grignard Reagents can not react with themslves, but it can react with water and carbon dioxide. So you shuold use it as soon as possible.