Hi there K.,
First I wanted to say kudos to you for being so diligent about breastfeeding...that is awesome. Now to answer your question, prior to baby #3 for me, I was told that at/about 12 mos is when the transition should take place. Then when #3 came along (seven years difference with #2 and #3), they said not to introduce cows milk until 13mos. So I'm not sure that it made any difference, but this was medical advice and WIC office advice. If you are able to, and can tolerate it, I would continue pumping for as long as you can. Nothing is better than momma's milk.
Bless your heart with nursing while baby has 5 teeth too. Teeth are the reason my first two were weaned at 6mo (well I started when they were 6mo). My girls were both biters. My 3rd (boy) I nursed until 8mo with teeth.
In the end though, there is NOTHING WRONG with choosing to give your child formula until the changeover to milk takes place. So if you decide to discontinue nursing, that is perfectly fine. Try not to stress about that. I made the decision to quit nursing at 6weeks with my 4th, and couldn't be happier about it. I was disappointed at first because I loved that bonding time, but Gabe is much happier on formula (he was sensitive to ANYTHING I ate). He has been doing great with formula, as did all of my kids after I stopped nursing. Just remember that formula is called "formula" because it is "formulated" to mimic breastmilk. Hope this helps dear!
B.