When is it Time to Let Go of the Baby Clothes?

I have two kids.  My daughter is eight and my son is six.  As many parents know, along with kids comes…stuff.  Lots and lots of stuff.  It’s toys, clothes, blankets and bottles.  It’s bottle heaters and baby monitors and booster seats.  Most of the stuff isn't being used anymore.  But we're not sure if we’ll ever need it again.  My question is, when is it time to get rid of the baby stuff that’s clogging up my attic and basement?

The problem comes from two different thoughts.  The first one is that we’re not sure we’ll never have another baby.  We are happy with our little family but we haven’t ruled out another little one.  So we don’t want to get rid of all of the things that we accumulated with the first two and find ourselves at square one again if we decide that we’d like another.

The second problem comes from the question, how good are these things going to be if they’ve been in storage for the last 6 years?  Are we going to want to use them with a new baby?  Won’t we want new things for the new baby anyway?  Chances are there’s better technology for the electronic stuff and better fabrics for the clothes and blankets.

Honestly, there's a third factor involved too.  It's the emotional attachment to these things.  They're the first blankets that the kids slept on.  They're the bottles that we clung to as we tried to rock our babies to sleep in the middle of the night.  How do we part with those things when they hold such incredible memories for us?

Do you have a rule of thumb that you use when it comes to purging things?  It doesn't have to be just baby stuff.  What do you do about toys and tools and stuff that’s filling up your storage space?