How many iterations?

I can't believe how many times I've gone over and over each ship! It shouldn't be that many. Mostly its getting a good idea on one ship and that proliferates to many more. One simple example is "I'm going to texture this part this way in Photoshop" simple idea, so what, looks great. But that's b/c the UV's on this ship works in Photoshop. Next ship needs to be re-UV'ed and sometimes that means redoing large portions of the texture. So what seems like one simple idea can have ramifications that become clear with experience. I continue to learn... when will I finally know it all?