NY Rat:
In my experience, too, the bags sometimes develop slow leaks over time. For me this is not a problem. If it is annoying, I just replace and repack.
I don't use these bags for survival food storage,... just to pack my small kit. In fact, sometimes I don't even pull a vacuum on the bag: I just squeeze out excess air by hand and heat-seal it.
IMHO the advantages are that the "container" can be as large or as small as you need it. I even have bags-within-bags: a mylar emergency "blanket", wire, and duct tape shrunk down suprizingly small in one bag (shelter); a few bandaids and some newskin packets in another; and everything else in the PSK distributed throughout the larger bag with the two smaller ones within. But my point is, with this packing approach you can cut/shape/arrange/pack anyway you wish.
A disadvantage it that, once opened, you need the machine to re-seal. Or, in the field, a bit of duct tape.
NOTE: where this vacuum packer REALLY is neat is for emergency clothing. A set of spare socks, polypro long underwear, even a waterproof shell, etc. etc. can be squeezed down amazingly thin and tight (and in a waterproof bag, of course). For gear that I don't get into except at a time of urgent need, I keep the stuff packed in the large (12"x ??") bags and stowed in my duffle bag or vehicle. TRY IT: you can compress a warm, dry, change of clothing into a package no thicker than a Brooklyn telephone directory.