Yes, none, any amount at all for any amount at all...assuming no akrasia, and as long as you don't mean 'right thing to do' in some kind of merely conventional sense. But that's just because, without quotation marks, the right thing to do is the formal object of a decision procedure.

If that's so, then your question is similar to this:

Would you infer that P if P were the consequent of a sound argument? If not, under what other circumstances would you not infer the consequent of a sound argument?