Almost certainly for any reasonably developed planet, if only for the very simple reason that a single office couldn't be easily reachable from more than 50% of a planet's surface at any given time. Descending to the far side would be easier, but for ascension you'd either spend a lot of time waiting on proper launch windows or consume a ton of fuel doing launches outside of the opportune windows. So, as said, if the planet is reasonably developed, you're probably going to get at least 2-3 offices up soon enough... and the most undeveloped empire planets are probably in lowsec anyhow, where we've had the run of our own offices for ages.