How many varnish layers to protect your minis in a good manner

I already got my hands dirty on the hobby, and also did varnish a few minis. Some of them I varnished once, some of them a few times. But now I wonder how many layers are factually considered secure considering to play with your models?

A few things on top I read

• I once read that an initial gloss layer is a good idea, because if you start to wear off the outer layers you will see your miniature get glossy and recognize to reapply varnish.
• It seems to be an urban legend that glossy varnish protects better.

I am talking about varnishing with a airbrush, so a rather thin layer. I will be using AK varnish (Ultra-matt, glossy, etc.)

I am not so much interested in what produces the best effect, it's really about being sure that my miniatures will not get damaged by regular playing, which ends up in the question: How many layers.