What ddawg said. ^
Also, if you installed new faucets, they probably have flow restricters. As a result, they're running less water than the old faucets, and it simply takes longer to run the cold water out of the pipe.
Anecdotally, my wife & I live in a big 2-1/2 story brick house. The main bathroom is on the 2nd level, and the water heater is in the basement. It takes quite awhile to get hot water up to the bathroom. The only real solution is to install a tankless water heater in the upstairs bathroom. I may eventually do this, but right now the cost makes it very unappealing to do so.