Store rooms are filthy. Factories' cleaning products are fierce.
I washed everything new except when we were in emergency mode and DH was sent to Mothercare for yet more things for DS2 to puke on 
Everything will be washed when it comes down from the loft, even though it was washed and vacuum packed when it went up there.
I wouldn't wash things too far in advance though in case they weren't used, so they could be returned/exchanged if necessary.