I'm just curious as to how many people out there actually do this. For the textures I use most often I have usually three different resolution variations. One for high res images (usually portrait) a med res (for full body images), and then lo res.

And even then I very rarely use a 4000x4000 res texture. The highest I usually go is 3000x3000. 
For most images you can't see a noticable difference.  I know some like to render large res images for easier postwork and that somewhat makes sense.

Another thing I have found that is misleading is poly count slowing things down. It does to a degree but for the most part its the texture resolution that eats up your memory.  
For about 50,000 polys you use somewhere in the range of 10mb of memory. For a 1500x1500 texture your eating up around 25mb of memory. 
For raytracing the higher poly count will slow down rendering because of all the angles to calculate the light being bounced off of. But the initial load is all on the textures.
With hair you will find that if you go to object properties and turn off seen by raytracing it will significantly speed things up.

Then there is the relationship of "slowing down" and memory usage. By slowing down I dont just mean render times, but how responsive the program is as well. In P6 if I have high res images loaded it becomes almost unusable at times. (click and wait, click and wait).  So If I use lower res images then the rendertimes may not change a lot but things are much easier to manage and poser isnt having to write to disk for memory constantly. 

anyway just curious what others think on this topic.

Handle every stressful situation like a dog.

If you can't eat it or play with it,

just pee on it and walk away. :-)

....................................................

I wouldnt have to manage my anger

if people would manage their stupidity......