Like for many things, I gather experience book after book. After preparing an history book, I realized that to use a hyphen for J.-C. (70 occurrences of it in one book) was NOT a nice idea.
I have no idea how many words of this kind I may find and I am really not sure that all occurrences of .- should deserve the same treatment. That's why, I thought first to add them one by one.
But, in fact, I realize there does not seem to be a very big risk to try your solutions. So I will try them. Thanks for them.
And enjoy a Merry Chrismas.