Don't know how you are getting on Raf or if you are still visiting the website. Any treatment should be started now or very soon if any supers for human extraction are off the hive.
Vape at any time of the day and repeat at 5 day intervals where one will see the mite drop if a board is inserted underneath.
I started my vape treatment on Monday and yesterday for my colonies with a follow up vape at the weekend and then end of next week.
I tend not to bother monitoring mite fall closely as I know there will be mites and often a lot. That said I do initially for the first 48hrs monitor the garden hive mite fall, so far 24hrs = approx. 100 dropped.
At the third vape I will put the boards on to monitor mite fall to decide if an extra one is needed, I will revisit the hives mid October and carry out a one off vape to monitor in case of reinfestation which isn't uncommon and may catch some off guard.
Beeks will lose colonies over winter and we have seen indications of varroa as the cause depite varroa treatment in Autumn, some think that the job is done with the initial treatment and become complacent but with a reinfestation it will catch some out.
Reinfestation can come from non treaters who neither monitor their colonies or simply don't bother and allow the fittest to servive, both camps do little to help beeks who manage their colonies in a responsible manner. Bees will forage and mix so mites can jump host.