You can leave the batteries in the 5er, but you need to make sure that the batteries are full of water (top off the battery water prior to the final charge) and FULLY charged when you disconnect the cables. I checked your weather for Puyallup Wa (I hope that is where you are), and your winters are rather mild compared to a lot of the other locations. Disconnecting and leaving your batteries in the 5er should be just fine. I always removed all the cables from the battery(s). Tagging all the Negative cables and tagging the Positive ones, makes it a lot easier and less confusing come spring. In cold weather the % of battery discharge is greatly reduced, so leaving them is not an issue.
This is one of those subjects that has a lot of followers with different beliefs. I can only tell you what we did up north at the Illinois/Wisconsin line.
I forgot to add the weather stats for your area
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