Recommended thickness of enamel?

Hello. I am using a super opaque Milton Bridge ODW1. I want to do miniature painting on this (hence it should survive 5 - 7 firings in the kiln).

What should be the thickness of this enamel layer? 0.3mm? 0.5mm? I am using 0.8mm thick discs.

Im concerned if there is something as ‘too thin’ of a layer. What are your thoughts?

Thank you.