John,
It's actually encouraging to read that even such skilled modelers as yourself have trouble with motivation from time to time. I'm working on a Glencoe 1/74 scale Martin MB-2. I've been working on it since May of 04!
I never took a lot of time off from the build, but the kit has taken a ton of work to get it up to my standards. I think I've finally hit the point where I can see it finished -- the light at the end of the tunnel, as you put it.
Regards,