There is no specific number for all cases. But it seems like timing sensitive people can feel jitter problems at about 5ms. But it is best to try to offer better performance that that if possible. The jitter of one product is almost always not the only factor. Most devices are connected to other devices, transports, or systems that contribute their own jitter. A target of 1ms for a single process is very reasonable for many functions. But this is all really oversimplifying. Much more info is needed to make decisions about what is good enough. Sometimes you don't need to be that precise and other times higher precision would be useful.