FS ~ Went back to read your five wax blends. I may have missed something but do you have each scent in each of the five different blends? Like, is Sunshine in 5 different blends and doing the best in blend #2 or do you only have it in blend #2? It seems that one is doing a good job for you in longevity. So, it makes me wonder if the tart burner is more of a factor than I originally thought. It does seem to factor in here, possibly. The ones I have that heat by tea light seem to have better HT than the ones that I plug in. I had begun to wonder if my BH&G electric tart warmers were doing something to the tarts. It seems lately the melts are not lasting as long as they did. I am using up ones that were made some time back, which could also be a factor. Will be interesting to see how this goes along in your tests. I don't have tart wax here at the moment or would have a notion to fire up the same FO in each of 4 blends twice. One to melt in the BH&G warmer and one in tea light warmers. The two BH&G warmers that I use the most have the light bulb very close to the tray where the melt sits. It could be burning off FO....or not.