Yes - you can freeze them, actually when you order frozen feeders, they are CO2'd then frozen. I prefer not to have to feed live and have converted most of my snakes to either f/t or p/k. But I have a small collection compared to most breeders (only 20). I've just begun raising my own rats, so I have not gone the CO2 route yet, but will soon, I still have a freezer full from my last order! I have two girls that eat live small rats and wont convert and one male that is 50/50 on live and p/k mice. I do the neck snap with mice or very small rats, but it's harder to snap the neck on a rat especially the medium size ones! I've also hear you can pull their tails off without snapping thier neck (ouch) which is why I'd rather to CO2 them. Also I get a little creeped out having to snap a bunch of necks. Anyway - I hope this helps.
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Tosha 
8.10.0 Ball Python (Harry and Fluffy and currently un-named)
0.2.0 Feline (Pippen and Pandora)
0.0.1 Dessert Tortoise (Pope)
7.9.5 Fish (1,2,3,4...)
0.0.1 Frog rescued from pool skimmer
0.0.2 Lizards rescued from pool skimmer