However there are times when making decorative items the size does not matter as much. And we do not want to take forever to print. The time to print and material used is dependant on the volume of the finished product. There are times when we can reduce layers reduce or eliminate fill this reduces print time and material at the same time sacrifices strength. .  But what if we want or need to keep strength high but drastically reduce printing time and material use. Case in point I want to print Thing # 832989 aka the Caterpillar 777F dump truck model for my grandson. Colorfab printed this model in NGen  so I am wanting to do the same.  I slice the the part and one tire will take 46 Min and about 2 meters of material to print.AARgh.   
I do not want to take forever to print this and  ngen being a bit pricey $38 for a 750 g spool  I really want to save time and money on this print.

So here is the beauty of MATH. I resize the part to 75%  .75^3 = .421 so the volume the truck is less than half the original I Am using half the time to print and half the material.  In retrospect if I had taken the cube root of .5 i could have used a .79.37% scale and reduced the volume by 50%.
The moral of the story here is making a part a little smaller (21% smaller) one can cut time and material in half. 
Size does matter when it comes to printing time and material usage.
Hope this helps others.
Tin