I often make the extra variable as I think things out and then decide later whether or not to eliminate it. I usually make them go away unless the next line gets too long to read.
Every variable is a floating hazard to navigation in the rest of the scope. Somebody might decide to use it for something else. It's also one more
unit of information the reader must comprehend and then go find all references to for understanding. These are tiny negatives, but some people are quite sensitive about them. If you decide to keep it, making it final would express your intent that it's only set once.
And if you're able, change the ridiculouslyLongMethodName to something meaningful but easy to digest. The name you were about to give the variable might be a good candidate.
[ November 16, 2007: Message edited by: Stan James ]