Well, then, I stand corrected it's not 15 days, it's 5 days, which is still 4.99 days too long for my preference.
But the comment about drones being able to enter any hive interests me a lot.
My three hives are literally stacked against each other. One hive (the middle one) is teetering on needing treatment according to the seasonal NYBeeWellness and the OTTT thresholds. It is a huge hive (3 deeps plus 3 mediums) running at full bore. In the circs., I felt my routine mite drops could overestimate the mite status due to the huge bee population (since mite drops don't count mites/bee, only the number of hapless dropees/day), so I sucked it up and did a roll. The roll numbers showed a lower but still high-side range so I'm practising watchful waiting, and doing more testing.
The other two are completely different though. One is clearly lowish 3-4 mites/day drops, and the other one often has no mites/24 hours, though usually has one, sometimes two.
If drones can move among such closely-placed hives freely why wouldn't my mite levels even out among the hives? Especially because the almost-no-mite-hive has an attractive drone club-house as its upper story. The next-to-top box (now above the feeding rim, but below the quilt box) is basically empty except for a tray of old honey comb being tidied up. During the warm months it is chock full of drones just hangin' out together. My husband dubbed this box, "the Man Cave". I was such a clueless noob last summer that for awhile I thought the "Drone Concentration Area" was something similar to what I had just cobbed together to handle the honey-mess left-over from the cut-out. I thought I was pretty clever to have "re"-invented such an established piece of bee equipment all on my own. (If you want to know how truly clueless I was, know this: for at least a week I thought I had a whole hive full of enormous fat "queens" only to discover they were actually drones. Who knew? Obviously, not me because it took me 47 weeks and 3 days to finally find all three of my "real" queens. It must have been a running joke among my bees about how easy it was to conceal them from me.)
What keeps one colony practically free of mites and the neighbor in the next apartment over under constant threat from them if the boys can bring their mites in whenever they visit? Of course, my bees are all unknown origin swarm-mutts, but still.
Enj.