Spring build up is very important when do you get the hive to foraging stage. They have time but as you know all yield period is valuable and that not the question that late season...
To 2 box winterd hive it takes 2 months. To under one box hive it takes 3 months. When the hive is n foraging condition, it swarms. Then it takes again time to get the hive into condition.
You say that you have long a spring and a long summer. But when do you have main yield periods and are the hive in condtion to catch the yield. You have 4 yeild months. You cut 2 off and you have less than in Finland.
Yes, I read between lines because very few here speak about pastures and yield. Some hives are on back yard.
First brood cycles are really important because they are investment to next brood cycle. And that cycle will forage after 2 months after lying. It is really a big mistake to destroy or disturb the hive. And what is basicly the reason. Just someone told and you must try?
Of course if your hive is mite porriage you must do something but now it almost winter and you are planning that you will have so much mites that you will... that is nonsence. Mites are just in your head.
In the middle of summer there are moments when you may do mite killing if it is necessary.
* cutting swarm fever with false swarm
* in late main yield you take the queen off and mostly bees gather honey more than they raise brood. Mites are again free to be killed.
To me the spring build up is the most important. It is a door to the honey summer.
During my 29 varroa years I have never needed to disturb spring build up for varroa. 1987 I got a swarm which was full of mites. That I handled with Perizin.
I wonder what is really need in Britain to kill mites during spring and during honey yield. Is it just a toy effect? -- Yes, as adult persons of course you do it but why?