Well, we don't know his exact rank in In the Beginning. Brigadier General? Major General? Lieutenant General? Nor is his full title given in the series itself. (Full titles are rarely used in ordinary conversations between military personnel. Even a Lt. Commander is normally addressed as "Commander")
Once you're a general, you'll always be some kind of general, even if you do recieve a promotion. You can only become a different grade of general (entitled to wear more stars.) There is no other rank to be promoted to.
Also, the further you move up the chain of command, the fewer slots there are in each rank. So it isn't unusal for a carreer to hit, say, Brigadier General, and never advance beyond that, because not enough people die or retire for everyone else to move up. (Heck, given that top rank positions are so few it isn't unusual today for a man or woman to end a full twenty or twenty-five year career as a Major or Colonel, and nearly all naval carreers end well short of even a Rear Admiral's flag.)
So I don't find anything odd about Lefcourt's career. He almost certainly did get promoted between ItB and the series, if only because so many officers must have been lost with their ships during the war, but he'd always be called "General", so we would have no way to tell. /forums/images/graemlins/smile.gif
(I don't recall - do we ever see him wearing a given number of pips or stars on his uniform? If we do, I'll bet there is one, maybe two, on his ItB uniform, and three or four by S4.)
Regards,
Joe