Yes, like beads, you can't use too many Boveda packs, but you can use too few. So they err on the side of caution (and you buy more packs ;-) For a trip of a couple weeks I'd say one is more then enough, especially if the cigars are in cello.

BTW, misting the Boveda packs with distilled water makes them last longer.

I myself think that one pays an awful lot for the convenience of Boveda, and use the bead sheet sold by Heartfelt. The sheet takes up less room than beads, but you need more of it there is less surface area. (The amount of water held is the same, but the rate of humidity release/capture is slower).