The further apart the observers are and the larger their relative velocities the larger the effect is. There's nothing to stop the differential from being years in extreme cases.
For any speeds we'd be likely to be traveling, in system, it'd likely only be a problem for milliseconds if that. We'd still be able to correct for where things are as we approach them or plan to approach them.
Yeah, I was thinking only of in the Solar System. Beyond that, the primary bound on commercializeable space is probably spacecraft propulsion, which will take a while.
