What are you sealing and how big are the bags? For the most part vac sealed bags are for storage for no more than 2 years. If you are only planning on keeping the food for only that long then obsorbers are not needed. It seems about half of the bags will loose their seal in 6 months, at least that has been my experience. How long are your bags going to be kept?
It maybe more cost effective to use mylar. Foodsaver bags are expensive. Generic brand vac bags I have used dont hold a seal. If you putting away rice, beans etc go to mylar with an absorber. You can get from 1/2 gallon size to 6 gallon. They are even making zip lock mylar bags that have enough top so they can be heat sealed and once opened for use the zip lock can be used. I purchase stuff at the link below, I dont have any affiliation. They also have alot of information to check out. www.usaemergencysupply.com