On the one hand, you're totally right. Deciding to redo everything on a whim based on an inspiring mini that I'm relatively sure I lack the skills to replicate is probably a bad idea.
On the other hand, a lot of my marines are long past due to be stripped and redone anyway, seeing as I've had some of these miniatures for, like, a decade, and I was /not/ a good painter ten years ago.
I actually regret re-doing many of my older models. I had the money, I just chose to re-do them rather than buy new ones. Had I have actually done so, irrelavent of how bad they were, at least I might have finished an army in the last 20 years...
However I do also get a big kick from seeing an old 'favourite' model redone and looking the best I can make it (some of my space wolves got that treatment)