Fools. TNG lasted seven years, and continued for another year or so until Generations, when Deanna crashed the D. And even then, nobody said anything about a 'five year mission'. Had Riker not let a woman driver take over, it could still be going now.
I am fully aware of all of those reasons, but it is just incredibly inefficient imo. They could have used all that extra power/resources for something a hell of a lot more useful.
Btw i only have a single head and arse.
Inefficient? Why would Starfleet care about being inefficient? They've got pretty much everything they could possibly want resource and power-wise. So, all they've got left to do is go around figuring out ways to spend their practically infinite resources.