This is exactly how people end up N+1. I'm a one bike guy-- but not in a one bike family. My bike came equipped with 5700 105, so when I upgraded to 6700 Ultegra, the 5700 parts went on the wife's 4600 Tiagra equipped bike. The 4600 bits are destined for the bike I'm building for my son. Trickle down, yeah.