I do think this would be odd. Can you hardwood?

Bad idea. Just buy better quality carpet and do the standard 2x per year shampooing that is required to maintain it's warranty.

Sophie is right. Except that carpet manufacturers require professional cleaning via hot water extraction every 18 to 24 months to maintain their warranties, not twice a year. It would also help if you had a shoes off policy in that bedroom.

"When soiled" and that example pretty much shows that this household needs 2x a year rather than a longer time frame of a lighter wear environment.

It's not just soil. Frequent shampooing and shoes off policies reduce the severity of the problem, of course. A clean carpet always looks better than a dirty one, and soil particles cause sandpaper-like abrasion to the fibers. But traffic patterns occur as a result of constant wear in clean carpets, too. The constant traffic causes increased abrasion. That creates a permanent change in the fibers that alter the way the light reflects, making it look soiled compared to the smooth fibers in the lesser worn areas. That's why most carpets (and carpet cleaning companies) do not warranty against traffic patterns.

There is a brand of carpet called SmartStrand that does, however, offer a lifetime warranty on soil and stains, and a 10 year warranty for traffic patterns. At least they did 3 years ago when I purchased mine. Might even be 20 years. I should check! That warranty is precisely why we got the carpet, too. We figured that the very fact they offered such a warranty indicates a fiber that's far more resistant to breakdown. So far so good.

I would just go with your new carpet and just put a rug down to save the carpet in that high traffic area, rugs tend to be cheaper than a whole new room of carpet. :)