1 billions cells: useless?

Sarah Palin

hello, further to this:

http://www.cfdreview.com/articles/08.../1933248.shtml

one question is: is this really useful for design changes?

with 100 millions cells you resolve flow features < 1mm look at your ruler what is 1mm.

with 1 billion cells, could you be wasting 170 hours of computation for 1 run to resolve flow pattern of the size of a hairpin, whereas 17 runs with 10 times less cells at different speed or design you give you a better understanding of the thingy you are looking at.

especially for a boat which need to run under infinite conditions of wind/wave/sail choice.