The tales ends with- "and he carries their four heads eastwards with him, until he reached his house before it was morning."
I'm not sure if there is any reference to the location of Conall's house in the Ulster tales but I presume it was in Emain Macha. If he left Belcoo at night and arrived before morning, how long would it take him to get home? If he was in a chariot he would be travelling about 10 miles per hour or maybe 15 miles an hour on horseback.
Telly addicts unite!