Cool. I'd stay away from anything that's just an open volume with no baffle or filter media (which sounds like you are).
Looks like you're in MN. I'm in SE WI, and in the winter months, I was draining about 12oz from my can every 1000mi (mostly condensation). Assuming similar operating conditions, perhaps you can estimate 1 oz accumulation every 83mi in winter conditions. Might give you a rough idea on how often you might need to drain a particular can (based on volume).
Keep an eye out for total volume vs effective volume. The RX Monster, for example, is considered 20oz, but I believe I read the "effective" volume is 16oz.
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