Are you talking retire-retire, or do something else making money, but likely less time and far less money-retire.
First, I'm assuming you've confirmed that you can be on your SO's insurance, even though you aren't married. Second, you mention moving to Europe for a bit or slow travel, but the SO will still be working. So you will be in Europe or cruising around the US alone, but on her insurance?
Will you still be contributing the same amount to the household? That would mean you are paying some of the rent, but also paying for transportation and lodging.
Am I misunderstanding?
Personally, I'd have a hard time not staying on for one more 6 month stint.