I carry 2 UMC's with me. Sounds like overkill. I had a nasty scare at 2 weeks of ownership, where my Original UMC Started Acting up. mknox actually helped me out with a temporary solution to get it working, and Montgom was kind enough to offer the use of his for the weekend if I needed.
The reason I carry 2, is I realized, If I'm in a area that had no public j1772 stations, I'd be Up a creek without a paddle if my UMC failed. Where I am every weekend, my Family's business is the only high powered charging location for ANY EV within 60+ miles. If my UMC fails, and I have less then 60 miles (A Nissan Dealership with a 30 amp 208v Leaf J1772 station is the next closest), I'd have no way to charge (as family's business uses a NEMA 14-50 instead of J1772). I'd need to have the car towed to a Nissan Dealership, or whatever the next closest J1772 is to then charge.
I am in the high mileage club (13,000 miles in exactly 5 months of ownership to the day), and even though charging at night is enough for over 99% of all my driving, it's that 1% that sneaks up on you when your not paying attention. At the vary minimum, keep your J1772 adapter with you just in case.