I've started buying my base malt in 1kg bags to try and keep it fresher, worth the extra couple of quid IMO.
I find one of the online suppliers will batch pack your order so if ordering 3 x 1kg of one grain will send you a bag with 3 kg.
Anyway, I guess just worth checking with a particular supplier before ordering 25 x 1kg bags.
Good idea to keep things fresh though.