What is the correct way to manage leftover elites? Should they be kept home for additional defence, or should they be out at all times?

As background, I usually send enemy defence + 4% as my offense to break, and whatever leftover elites I have left, I keep at home for additional defence. However I was told that I shouldn't keep the elites at home, as they can be hit by attackers which will kill my offence, and instead I should be sending out all elites either via oversending / conquest attacks and/or bounces, with the aim of having 0 elites home at all times.

I am a bit confused as to the merits of the latter strategy, especially given oversending / conquest brings with it additional casualties which could potentially outweigh the elite loss from them sitting at home. It would be great if someone could shed some light on this.