Generic battery Powerbook : Manufacturers Date

[aholeinthewor1d]

I'm looking for a new battery for my powerbook and i was reading around different sites to decide if i should buy an apple one or a generic one. On one site someone said to be sure to ask the manufacturers date of the battery because you don't want a battery that has been sitting on a shelf for 2 years. I'm wondering what would be acceptable. One seller on Ebay said the date was April 07 but its not on the packaging it was just on their invoices for the batteries. what should i look for with the manufacturers date. how old?
Thanks a lot