(UPC) Uniform Plumbing Code calls for 60" (five feet) on a 2" drain.
I don't know what they use in Canada, but the reason to limit length, is to prevent the trap from siphoning.
The goal is to have some air breaking the siphon. By extending all the way out to eight feet, you get near the point where it becomes an S trap.
The first goal, should be to maintain a trap seal.