They tolerate some crowding, but eventually you'll need to repot, if only to give them some soil to suck nutrients out of... although they can take a lot of abuse and benign neglect. They are incredibly easy to 'slip', to make new plants from cutting off the ends of existing 'runners'. Mine get moved around a lot depending on what else is going on with the 'chids. They do need fairly good light to grow well, but direct sun burns (at least the ones I have).
BTW, slipping the ends of all the runners not only will give you another plant (use multiple rooted slips to create one plant), but will usually cause the existing runners to branch. Since these tend to get really long and stringy, having it branch makes them more attractive.
PS - Clean the leaves! These guys can't purify the air if you don't let them breathe!!!