In my years as a La Leche League Leader, a mother, and writer, I have found that as parents, we have many, many different approaches to limit setting in different situations.
There are parents who strictly regulate their children's days, setting limits for most activities, so that children know exactly what is expected of them and what is allowed and okay.
On the other end of the spectrum are parents who feel that children should find their own limits, be allowed to explore the world more freely, and discover on their own where their limits should be.
In all actuality, most parents probably fall somewhere along the curve between the two.
When it comes to breastfeeding a child after they've turned three, the story is no different. Some may assume that because you've allowed your child to nurse until they have turned three that there couldn't possibly be any limit setting in your household, but I have found that this is not always the case. In fact, some mothers have found that limit setting was exactly what they or their child needed. Some families, however, have found the freedom of no limits on nursing to fit their lifestyle better.
What have you found to work best for you and your child?