We had a chase car when we were in our fifth wheel/ dually combo.
We traveled at least once a week though. After about 9 months, neither of us were happy.
A large part of fulltiming, was to experience it together. Even though we had UHF radios to keep in contact, and tak about stuff we saw, it wasn't the same.
40 mpg vs 15 in the dually, and the ease of parking were the great things. The mpg in the chase car, since it was paid for, made up for the extra cost of registration and maintenance, and kept the miles very low when we sold the dually, decreased truck maintenance, and wear and tear.
The downsides... if you move a lot, and enjoy your spouse, it isn't great. Certain parks, especially State and County Parks had an extra vehicle charge... usually $7 a night, which greatly increased camping rates.
If you plan on being in one spot for quite a while, which it sounds like you are, it's extremely beneficial. If you move alot, not so much.
Best of luck with your decision.