The problem with prior history is that it assumes there is a four year cycle when it comes to careers, which works well for lifeforms and in particular our frame of reference (I would say it would be long for us, it seems the cycle length of careers has shortened in our generation); at the end of each cycle, the person must either have been promoted, or convinced the higher-ups of his or her value to stay on for another four years, or they have to find a new job.
But is that applicable to a robot? If we go by classic stories that feature robots in them: let's choose Asimov and Star Wars.
In Asimov, robots are property. In the case of R. Daneel, he and other Spacer Robots are treated much better than on earth. Yet, do they go out into the Galaxy and work odd jobs? From memory, I seem to recall Daneel being indentured to a master (was it Gladia?). I have only seen the movie of Bicentenial Man, but in it Robin Williams' Robot character is basically the property of a kind and benevolent master, and stays with him for decades (until the master dies, and in his last act grants his Robot freedom... like a slave master would grant his slave, essentially).
With Star Wars, robots are almost always seen to have a purpose of some sort. Probe droids, combat droids, interrogation droids, etc. These don't exhibit any personality traits, they do their job and either leave or get destroyed by the heroes. However, we do have two robot characters, R2-D2 and C3PO. These two are quite a pair, but they've been more or less together for several decades. In that time, the number of their masters didn't change all that much. I think it went Anakin-Bail Organa-Luke, where it's stayed.
One thing about robots in SW is that they undergo periodic memory wipes to prevent quirks from forming (think of a the three laws as applied to a combat droid or an interrogation/torture droid). The longer a droid goes without a memory wipe, the more autonomous and independent-minded it will be. (note that Artoo never received a memory wipe throughout the whole saga, and he was far more rebellious and "I'm gonna go here, now" while Threepio was more of a nancy boy: "I've been told to sit here and that's what I'm gonna do - wait! Don't leave me artoo! Come back!!!")
So what does this imply? Well, the standard prior history rules say that a human or other lifeform starts his adult career at 18, in some cases 14 (Barbarian and Belter classes. I also house rule that the Noble, Rogue and Psionicist classes can start at 14 too). The first 14-18 years of their life is childhood, basic schooling, and formative years. How does that apply to a robot, who don't have the biological basis for childhood and so on?
Well, perhaps the first years of a robot's life is actually service to a particular master. Maybe two decades long. After that time, the Robot can spread it's wings and travel the galaxy and THEN begin having 4 year terms like a normal person. Thoughts?
