JR, tkae this with a grain of salt, as I'm currently not using an airlock, so everything I think I know, is just from reading, speculation, and from not paying enough attention to that part of things when I worked for other shops.
I think it's a must have for any shop that is constantly making chips. It also opens up other opportunities for handling the chips after the airlock. You can just drop them into a dumpster or barrel, or you can blow them into a trailer or bigger dumpster.
If it's running whenever the dust collector is running, it bridging shouldn't be an issue. Putting it on a timer so it runs for a bit might not be a bad idea though.
The amount of air coming back into the cyclone won't be much.
I don't remember any issues with ice and snow at the shops that I worked at. This is minnesota too.
I'm probably just defending my position on this, I bought a 12" Torit airlock for my bag house for $200. It is a wreck. The gear box is most likely not salvageable, it's missing the motor, it's missing the chain, and I'm guessing the bearings need to be replaced. It needs a compete rebuild.
I'm just going to drop it off somewhere local, and have it rebuilt entirely. I think that airlock is about $3k new, I should have less than $2k into it when done, and I should have a basically a new airlock.
Something I have been considering is instead of running a gearbox to get it down to 40 rpm, and another reduction through a chain to get it down to 10 rpm, I'm kicking around putting a brushless motor on it and deleting the first gear reduction. Less moving parts, plus the ability to adjust the rpm a little bit to better match input. At this point that is just a thought and I haven't dug into it any deeper.
Another thing to consider is a grinder for your scraps. If your sucking ground up scraps and drops out to the cyclone, and blowing them into something else, your handling of waste should be dramatically less. Just blowing ground up bits into the cyclone likely isn't saving you anything if you have to handle it again.