? ? "About the efficieny, I didn't mean affecting the application of the simulation for, I simply meant the 'spent time' of accomplishing the simulation(s)."
That is what I meant too.
Sometimes combining a few circuits in the same LTspice simulations makes it very slow, but sometime it doesn't.? If 3 circuits in the same schematic page make LTspice run 3 times slower than each one alone, then it is not worse than having 3 separate schematics and running them one-by-one.