I am sorry I wasn't able to respond in this thread earlier. The formula that I use is what Beekuk published however, for the patties I have started to add veg. oil to the mix. I found that this keeps the patties softer for a longer period. Right now I add one cup in the cement mixer formula and haven't broken it down for the smaller batch mixes but hope to post that in the near future.
The way I treat is as follows. Early spring (as soon as it is warm enough to take liquid feed) I feed two rounds from feeders (I use hive top feeders, one hold a gallon and the other 4 but it makes no difference). These have all three EO's, Lemongrass, spearmint and thyme. After the two feedings I drop the addition of thyme and continue to feed till the first flow with only lemongrass and spearmint (basicly a homemade mixture of HBH). In the fall as soon as the supers come off I feed the same way with two feedings of thyme in the mixture. Depending on the flow of the year this can be a 2:1 feed mixture but it really doesn't matter if it's 1:1 or 2:1. Then as the weather gets colder I switch to patties and will run patties with Thyme as well as the other two EO's until it is too cold to feed.
Results - Since starting this three years ago I have had no mite problems at all. During the first year when I made the switch, hives that had a heavy mite load I was able to get under control by "misting" each frame in the hive with a 1:1 mixture with the three EO's as in the formula. This knocks down the mite population quick. Subsequent feeding with thyme will take care of any mites that were in capped cells after they emerge. I have not had to mist any hives for the last two years, except some nucs that I purchased to get my numbers up. Misting nucs is a good way to start them out. You won't have to worry bout a mite build up after you hive them. I would suggest the same with a newly installed swarm since some swarms happen because of a huge mite problem in the parent hive. Also, I do not have honey supers on when using thyme. I doubt that it would be a problem but I find that hives that need attention or probably shouldn't have supers on anyway.
Negative results - I have seen no negative results from feeding thyme to the bees. At first my formulas were a bit strong and there was a little bee kill or "drunken" bee syndrom as I like to call it from the concentration of the EO's. By trial and error I have reduced it down now to the most effective with the least amount needed, at least according to my results. Note, I am not a Randy Oliver and have not done the extensive lab credible results that he does, my results are from observations and the heath of my bees alone. (BTW - my initial interest in thyme and it's effectiveness came from reading Oliver's initial tests with thyme awhile ago.)
Conclusion - Overall I have been more than happy with the results from my use of thyme and other EO's. My hives do very well and have no mite problems. Issues with Foul Brood, AFB and EFB are minimal and I contribute this to the bees being and staying heathy. When I do discover a AFB infection those frames are burnt.
Other things that I do to maintain healthy bees is rotating out frames and removing any frames that I suspect are contaminated (with anything). While there is a cost associated with adding new frames, I have found that doing so really cuts down on how far a hive will drop before I notice it. I was noticing that bees would avoid frames after awhile, no matter how much I tried to force them to use them. The bees are smarter than I was. So now I pull the oldest frames (usually between two or three in a box) per year. This way my oldest frames eventually will only be 4 years old. The costs of rotating frames pays off in better bees (at least in my case) so it is one of the things that I recommed as part of managing heathy bees.
Any will try and field any questions on PM that I get. Good luck to all.