This is related to the "Pause Boost" suggestion I saw on the list on ideas previously submitted.
I suggest a modification or addition to current boosts on barracks or spell factory, where for a few more gems, the remaining boost time will only count down if troops or spells are actively being produced. IOW, the timer stops if camps are full or the build queue is empty.
I don't often get a full two hour block of time where I can play and take full advantage of boosts. Even when I do have time, I often get interrupted and need to set the game down for a while, and end up wasting boost time. If I could spend 12~15 gems instead of 10, and get full use of that two-hours of boost, that would be worthwhile to me.
