Question for The Etiquette Goddesses

kevinandmonica2011

So... we sent out our invitations earlier than suggested (holiday weekend, graduation weekend, prime time travel)... anyways... we have received a few checks back with the RSVPs.

I know that it is improper to use wedding gifts prior to the wedding and I really do not feel right cashing the checks prior to that date.  On the other hand, I don't know that it is a great idea to have them sit here for another 3 months then deposit them (I can't remember 100% but don't some checks become invalid after 90 days... maybe I am wrong here).  I also don't want the people who wrote the checks to have a deduction from their account 90+ days after they had written the check (and likely forgotten about it).  I get annoyed when I write out checks for bills and they are not deducted lickity split. 

Thoughts, ladies?