I've been adding syrup weekly to my hive top feeder since April 17th. The previous syrup has never been completely gone, I've just poured more in to replenish. I'm concerned about the ongoing effect of mixing new with old. I certainly wouldn't do this with a container of milk in my refrigerator -- but short of having a spare hive top feeder I don't have much of an alternative.
I'm curious about what other beeks using hive top feeders are doing? Should I have spare feeders and swap out each time?