That's great, except your logic is flawed.
With the gate closed, one of the two seals has no contact with the PG solution because it is on the other side of the gate, so you're not helping yourself in any way. If one seal goes bad, you are still disassembling the valve to replace the seals. In fact, since you are leaving one seal dry and compressed all winter, that seal will have a failure mode greater than a seal left dry and uncompressed, i.e. its natural state, for the same length of time. So thanks, but your process doesn't pass the sniff test for this aerospace engineer. Keeping half the seals wet and the other half dry and compressed will not extend the maintenance interval of the valves.
