I've kept cube packs for a few months because I buy a few of them when they're on sale and they were perfectly fine. I have a big block right now that I just hack pieces off of and I've been working on it for almost 3 months. There's no freezer burn, but I vacuum seal it in a freezer bag. I've never had bloodworms go bad before, although it's not easy to keep them around long anyway since almost all of my fish adore them. Every peaceful little angel suddenly turns into a hellish piranha as soon as the bloodworms hit the water lol. The only time I've ever had a problem was when I went to go buy bloodworms, headed immediately home, hit some traffic, and they ended up totally defrosting and even heating up in Atlanta's 3 million degree summer heat. So don't let them totally defrost
Is it better to just get the dried type in my case?
This totally depends on the fish. Some fish are ok to eat freeze dried bloodworms, and some can't handle it. There's a lot of hate for freeze dried foods from people I've talked to. Some say it's low in nutrition, some say the fat content's way too high, some say they might expand in the fish's stomach if not properly rehydrated and cause bloating or constipation. I really don't know too much about it, but I just prefer not to take a risk, and frozen seems to be the best bet all around and WAY more fish are willing to eat frozen, ime, than freeze dried. I used to give my angelfish freeze dried maybe once a week or so, but once I started giving her frozen, I'm quite certain she actually scowled at me when I popped a couple freeze dried worms in the tank lol.
If you have any friends with fish, see if they want some of the worms and then just split a pack of frozen, or vacuum seal them in a freezer bag if you have a food saver. If they're in little squares though, they're usually sealed anyway until you open that square, so I personally don't think you really have to worry about freezer burn.