Your bamboo really should not need very much maitenance. You can cut out any culms that look unhealthy. You can also cut older culms that appear to be in the way of new shoots if you want. It sounds like the bamboos are healthy and you like the way they look, so I really would recommend just letting them go. If any new shoots come up any place you don't like, just cut them off and eat them.
Most of the time health bamboos don't really need pruning. Sometimes people prune culms or limbs to make the bamboo have a certain look, but it is not required for the health of the plant.
