In practice UPC will probably have some kind of fair use policy buried in its terms of service - your best bet is to go through those terms and see what you find. Fair use typically means they will start throttling you beyond a certain point. Most ISPs keep this reasonably vague (e.g. if your usage is in excess of what they deem to be reasonable, but no actual data amounts defined).

Not all ISPs have a fair use policy though, and typically you’re better off on large ISPs where your usage doesn’t really stand out that much.