I think it would be fine but I would bring it up that you may need others when you first ask him. That's what I did. I also told him upfront when I asked him for the first one that I wouldn't mind if he just changed the organization name/address/etc and keep everything else the same. Whatever he's going to say like good writer, good organizer, in the first recommendation is probably not going to change in the second, third, or fourth. So, the only thing that would change is to where it's going. The prof then made a point to save it so when I asked him later on in the year when things got more busy, all he had to do was pull up the "template" and change the heading and date.