Have 6 Russian hives that overwintered very well last winter and have now made two shallow supers each of honey. They start early and work late even on marginal weather days. I have other colonies of varing pedegrees [Italian, Buckfast] that are late starters and early stoppers and now have less than a full super of honey. Also I lost 4 out of 12 colonies last winter. Should I look toward replacing my loafers with what appears to be a superior producer/survivor?