The way characteristics are increased is a topic I've had reason to give some thought recently. My players have cleverly realised that an increase in characteristics is one of the most effective ways to improve their characters - especially in the long run. They also feel, still being in the first rank and having already trained their career skills at creation, that there isn't a lot to spend advances on except raising characteristics (extra wounds, stance pieces etc. are fun but not that substantial).
So, the thing I'm wondering about is how you have handled raising characteristics overlapping change in careers. Do you allow players to put, say, three open advances to fill up a career and then continue with two open advances in the next to buy for example Str 5? And in that case, how do you handle the cheaper "primary" buys since the characteristic might not be a primary one for both careers? I think I'll allow it, simply because it's a bit boring to force a player to buy an cha increase completely within a career, in effect excluding almost all other choices for that career.
Magnus