In a country where professional gun toters regularly have NDs after dozens or hundreds of hours of PAID familiarization practice. I have zero hope of ever creating achievable, universal, standards of any kind. And therefore, the correct answer is, "Whatever you deem appropriate, because I can't tell you what is appropriate for your life."
I vote we shitcan all the standards and just roll on with (not so) common sense. If you fuck up and ND and hurt/kill someone because you're a retard, get ready to defend yourself in court (at minimum civil court).
Why am I opposed to 'standards'? Simple. They are a gateway/tool to allowing or continue to allow rights suppression.