I'm all for phasing it in over 20 years or so. The problem is that the political staying power in this country seldom exceeds 8 years. I think in inches, miles and pounds. I can convert mentally, but it's still an extra step. I could care less about gallons or liters. Don't rip me off any worse at the gas pump, and you can use whatever units you want. Teach the kids nothing but metric, and make everything have both systems until we old folks die off. Then bury the Imperial stuff for good.