What you want to do is entirely possible, especially if your milk supply has been good up until this point.
Around 15 mos, my little one started daycare. Before that he had been cared for by a series of babysitters who came for a couple hours between his 2 naps and I would take breaks to nurse (my studio is in the house). He was nursing AM, before his afternoon nap, after the nap, and before bed. Once he started daycare, weekdays I nursed him in the AM and sometimes after school, and again before bed. I had no problems maintaining milk supply. Around 20 mos he stopped wanting to nurse in the AM but still wanted bed time nursing and some afternoons.
He is now nearly 22 mos, and sometimes forgets to ask for bedtime nursing. My milk supply is definitely less, but enough for his needs and I don't usually get engorged at all. About a month ago, we went for 3 days with no nursing. I thought we were done, but on the third night he asked and I said, "I thought you were a big boy." He said, "NO. Baby." I still had milk (after 3 days I was feeling a little engorged--like I used to after 3 hrs when he was tiny). I'm following his lead for now, and hoping/dreading that he will be ready soon.