LP-E6 shelf life

[Tristan944]

I have a new, never been opened LP-E6 battery. I don't intend on using it for several years. How long do these batteries stay good unopened?

[neuroanatomist]

Not a good idea, IMO. Li-ion batteries need to be used frequently to maintain performance.  A typical Li-ion battery will last ~4 years or ~300 charge cycles, whichever comes first.

[Mt Spokane Photography]

All batteries self discharge, but Li-On batteries have a circuit in the case that shuts down the battery when the charge level gets low.  It is then dead and cannot be recharged.
I'd expect this to happen in about 3 years or less, depending on how long it was stored before you bought it..