Do Proportioning Valves Wear Out?

I am in the process from converting from 4 wheel drums to 4 wheel discs. Based on my research, I wouldn't stick with an old prop valve. I'd recommend getting an adjustable prop valve, like this Wilwood I picked up. In the long run, I think you'd be better off, especially if you route all those brake lines and you get a car that locks up the rear before the front. http://www.summitracing.com/parts/wil-260-11179