How long should records be kept?

I'm the Exec Sec here and happened to look into our ward's filing cabinets. We have 2 cabinets FULL of paperwork! I have found Food and Clothing requests from as far back as 1997. At what point can I start shredding old documents?
Is there a specific time like taxes? (7 years?) Storage is at a premium!

See the Record retention article.