Yeah, IC time is hard to gauge but we determine it by various factors noted in threads.
For instance, if you are talking about building a big ship, the main question I ask is "How long the group doing the building has been around?" (both OOC and IC).
Because XYZ group suddenly appears at TRF doesn't mean the planet, people, government, etc.. just appeared out of nowhere. IC, they had to come from somewhere so I usually like to think of XYZ group as simply insular and not yet on the galactic scene...more self reliant. Not with the resources to build a large fleet. Small planetary defenses, ok. But of course, even that depends on what your roleplay with regards to group before it's "coming out of the closet" on TRF. For instance, if you roleplayed that the planet just came out of a civil war and one party won and wanted to push the group into a galactic community (or interact on a galactic level with their neighbors), then they probably would not have concentrated too much on planetary defenses as they were fighting each other for political superiority.
Other factors would be the size of the ship, sophistication of the ship, etc..
What I see sometimes is people making R&D's and then roleplaying the R&D but this in itself does not constitute he owns then IC. A person can R&D (and roleplay) 20 ships and only have one planet. It wouldn't make sense that they have the resources to support said fleet. Then they go on a planet grabbing spree and assume that when they have completed a second or third takeover, their fleet automatically expands. Unfortunately, the planets taken are taken in the "present". The big ships take time to build. We let people fudge a little because there really is no rule other than common sense.
What really helps is if the group/person actually roleplayed character stories that tells what's going on with their faction. A "filler" story that adds credibility to the claims made for fleeting. If you try to rely on simply R&D and planet grabs and try to fight in the present, I think you'll be hardpressed. People like to rp that everything runs smoothly, ship production, droid production, etc.. and nothing runs smoothly.
So what helps iron out the kinks is how long your group has been around at TRF... so even if stuff doesn't go smoothly, you're around long enough to find those missing shipments of durasteel that went to a planet on the other side of the galaxy.. :b