Do whatever works for your baby and you. Some people think you need to get the kid out of your bed to night wean and that is not necessarily the case. There are plenty of ways to night wean and have the child continue to sleep with you. It's up to you what works and what you are willing to do and put up with.
Nurse him to sleep then when he wakes in the middle of the night just rub his back and shush and see if he'll go back down. Then nurse in the morning as much as he wants. Or you can wait until he is old enough to understand that once everyone is sleeping, he can only nurse again when the sun is up. Personally, I just waited it out and eventually my son just stopped nursing at night on his own and slept through the night. The No Cry Sleep Solution book has lots of ideas for how to do this gently.
I don't buy that night nursing causes cavities. We brush his teeth every night and most mornings too (he does and we "help" at the end) and he has always nursed at night and his teeth are fine. I do know other moms whose children had early cavities and they stopped nursing at night, did more brushing, and it didn't matter. I think it depends on the health of the teeth which is unfortunatly genetic.
If you already know you want to nurse at least 12 mos, you can do that either way. Nurse on demand all day and night, or nurse on demand during the day and not at all at night or limit night nursing to when he is teething, sick, or really seems to need it.
Also some kids do fine with mom deciding when to wean and others do better to wean on their own. They seem to need it longer and their attitude is better if they get to decide when they are done. My best friend and I were both nursing our firstborn boys (born 5 days apart) and we had different attitudes. She wanted to wean at a year while I was fine with letting my son choose when he was done. Her son did NOT do well with her attempts at weaning. As she tried to eliminate feedings, he retaliated with tantrums and hitting and refusing to sleep until he got it. There were a lot of struggles going on! When she realized his will was strong, she went back to nursing on demand which meant more feeings at first until he knew he could get it when he needed it. Then in a short while HE dropped a feeding during the day and eventually night weaned himself. She had to give up trying to control everything, which is a good lesson moms have to learn! (Especially if you want 3 or 4 kids!) He night weaned around 18 mos, nursed until he was 2, and started sleeping in his own room at 2 1/2. He is still a strong willed almost 3yr old!
On the other hand, I am still nursing my son who is almost 3 because he really seems to need it. He night weaned himself at 22 mos and still sleeps with us. We've had a toddler bed in our room since he was 15 mos when we thought he might sleep in it. I had to let him choose to sleep there on his own, he is very strong willed (like my friend's son). If I put him there for a nap (like when he falls aslep in the car and I move him there), he wakes up really mad! But if I put cool animals and books over there, he might sit there and read his books and decide it's OK to sleep there. He knows he can join me if he needs to. He slept there for a whole month, going over there on his own! But for some reason is back in our bed. But we are having other issues too (he wakes up screaming a lot) and I want to comfort him through that until we figure out what is causing that.
I think it's important to keep your bed open for a child to join you for sleep if he needs to. Sometimes they transition to their own beds easily if they know your bed is available when they really need the comfort. If they think it's off limits like you are banishing them to their own room and are not allowed to come back, they might fight it or be scared. You never know how things effect little brains. But it's also good to set boudaries like no nursing unless the sun is up. Or if you don't sleep well with a kid in your bed and you need your rest because you work, maybe have a matress on the floor and let them sleep there until the sun is up, then they can join you in bed for a bit. Just don't make sleep a scary thing they will dread.
Also the World Health Organization recommends nursing for at least 2 years. The benefits of nursing do not change at 12 mos so there is no reason to automatically wean then. The statistics are rising! More women are nursing longer and letting their children wean naturally. You can join the movement and be 1 of millions of women nursing toddlers!