The Heartfelt sheets won't last that long without being recharged somehow. I had asked Dave about them once, and he mentioned a window of about 10-14 days if you don't open the caddy too much.
I do love the Heartfelt sheets for vacation-length trips, though.
FYI, Ron at Cigar Solutions has small Boveda packs (7 or 15 gram) for the smaller caddies.
Link here:
http://stores.cigarsolutions.com/-st...Categories.bok
Can't go wrong for $2 apiece.