How far can light travel?

Answer 1

If light (as in photons) were in a vacuum, it would travel forever in a given direction.

In reality however, it is far more probable that light will experience disturbances (absorption, reflection, refraction, etc..) as it moves through space - thus, it's distance of travel is limited to some finite distance. I do not think that there is any good estimation for this realistic finite distance. Clearly, this finite distance depends on the situation of the light being transmitted, direction and regions of space through which it will travel.

add Recent observations of distant red-shifted astronomical objects indicate that their light was first emitted about the time of the Big Bang. So forever is a fair approximation. [Multiplied by the speed of light of course.]

Answer 2

In a vacuum, from one end of the universe to the other, unless it is obstructed by matter or trapped in a gravity well (black hole).