That could turn out to be a great idea! I keep a log in my iPhone of maintenance on the Expedition and guess which COP has been changed the most? You guessed it, #5 followed in second place by #7. In third place is #2 and unfortunately #'s 4 and 8 are tied for fourth rounding out the top 4
Man I hate those two firewall plugs/COPs especially if I can't take the time to allow the engine to go cold.
I keep my plug wench and all the sockets needed to change the Plugs/COPs in a $7 Harbor Freight tool box along with 4 plugs, 4 COPs, dielectric silicone, and anti-seize with me at all times while driving the Expy. I got caught on top of a mountain in NC during a Hurricane and when it cleared up enough to drive out of the forest, I found out I had two bad COPs and had to limp 50 miles to get to the first gas station, not fun. Damn weather forcasters, the only job you can be wrong most of the time and keep your job. The Hurricane was charted to keep going north before even thinking about making land fall, but after we committed and were in the mountains it speeds up and came straight inland.