It seems to be escaping out the overflow/over-pressure valve at the front-center of the engine block, triggering the low-coolant message about every 60-days during warm weather, when I add coolant it only takes about 1/3 gallon but that satisfies the low-coolant sensor for another couple months

 

Not normal but not unusual. The coolant system should not loose fluid and if it does there is a leak somewhere that needs repair. A number of auto parts stores will loan you a pressure test kit to make finding the leak easy. Careful selecting the reservoir cap from the many provided. You need one that seals the reservoir from the overflow system. I found that only the universal fitting worked. The leak problem should be evident under pressure.

I am not aware of an over pressure valve at the front center of the engine. The over pressure issues is handled by the reservoir cap.