there isn't really a set number but it's already the middle of the year so if you come in extend and fly out you should be OK at least for this year unless they change the rules again.
he is getting "the right visa". There is nothing wrong with coming in and out of the country. I don't want to live there. I do want to go there a lot. We did much the same thing. Several extensions jumped thru all the hoops to get a retirement visa and left right before it ended. It would be nice if we could go back and forth but we can't because of the 2 land border rule