CIM said:

I haven't done multiple training with boosts yet to see what is going on ... but I usually try to set my training size to an amount that I then usually only have to use one boost to boost it done ... that might help ... I probably will be doing some multiple training this week so I will see.

I use the same method when training, and it would indeed be nice if the chosen number of warriors in training would stay put until you manually changed it or left the barracks. I'm curious though... What do you mean by "multiple training"? -Cuz that sounds like something I could get on board with in a big way. XD

An additional thought... All of the sliders in the game should be made static for convenience, including the number/type of resources sent to the Stronghold or to clan mates and especially, the number/type of warriors you send to a tile. ;)