Queen losses were reported when they first released it which can hardly be attributed to out of date products. Myself and VEG an ex forumite used MAQS without queen loss but I lost colonies to varroa so stopped using it.I chose the right temp this year particularly for the first three days and all is well with my Qs. I did notice on the Beesource forum though that it is thought that there is a problem with using out of date MAQS (which by the way is unlawful), as the paper which acts as a wick deteriorates and releases the formic acid too quickly leading to an overdose.