M.G.
If he's not showing any interest in nursing just a bit before you are, then to me it's just for comfort/routine at this point - not so much that he's hungry - otherwise he'd be more interested. Would that be accurate? If so, then he may be ready to give it up entirely.
So what about having dad take over for a few nights and see how that goes? Or do you still need the nursing so you're not overly full by the next morning?
Or have dad read to your other son and during that time you nurse and then switch - hand the 16 month old to your husband, and you go say goodnight to your older son.
It might take a few nights of resistance before it works - just keep with it. You could go from rocking to just sitting in same chair/rocker, and opening a book and reading to him. That's kind of what I did. I kind of just picked a routine that I was ready to adopt rather than thinking of it as getting rid of the one I was done with - I try to morphed into what I wanted us to get to.
Let us know how it goes :)