How do ignition coils fail? Do they slowly lose their spark as they age?

I've got '78 F250 with a 351M and it seems to be slightly missing. Sometimes the whole engine shakes and trembles with the oscillation and shakes the whole truck.

I've rebuilt the carb (it needed it badly), replaced the plugs and wires. But, I'm not sure about the strength of the spark.

A week ago, the truck died on me. I thought it was the fuel, as it was rather low. But even starter fluid wouldn't catch. We jiggled the ingition coil plug wires and it eventually started up.

I'm about to go on a 1200 mile round trip in this truck, through some harsh terrain, and I'd like for it to be as reliable as possible.

Should I swap out the ignition coil just for good measure, or is that a waste of time?