If I'm attatched to the PoKéMoN or have a particular liking to them, I don't let them evolve until they have all their moves or I'm ready to let that image of them go. For example, my Cubone is level 65 but I still refuse to let it evolve due to being so to clingy to it. I captured a Marowak to fill in the Pokédex entry instead. Or like my Nidorina, I evolved it before hand just because I wanted a Nidoqueen. Then worked on what moves it could learn.