actually thought about it a bit more, and of course the tiny bits that make up the tail will keep the velocity of the comet, thats how they know the speed of meteor shower meteors, its the same as the parent comet/asteroid, and stays the same forever, unless something affects it, being in a vacumn and that.
They know the speed of the comet by its orbit, if it comes from further out/larger orbit they tend to be/are faster, and of a certain geometric orbit - meteor showers usually only come from periodic comets, like Halleys, or captured oort cloud numbers and never venture far from the sun.
So the tail will in effect keep following the comet (and it is never coming back i have read, or it has a massive orbit of some ridiculous amount of time, cant remember right now, out of the solar sytem kinda - also depends on the chemical composition of particles, maybe they might kinda further break down in size, from ultra-violet light even, bumping into each other ect.?
i could be way off here? dont take my word for it
