I don’t have a good answer for how to balance your oak influence between two lots, but there is a counterpoint, or caveat, to some of the preceding advice. I wouldn’t operate on the assumption that a longer time in a new barrel yields more oak influence. In my experience, the heavy handed oaky flavors are imparted inside a couple months. I imagine that is even more the case with half barrels. In any case, the new oak influence seems to pull back, or integrate, gradually over the course of the next year. I’ve never found that it continues to increase. There is a corollary school of thought that holds that the surest way to overshoot on oak influence is to pull the wine out of a new barrel too soon. I don’t know whether you really risk “arrested development” of new oak integration by pulling the wine from a new barrel before it has run through its normal trajectory, but that was a bit of advice I’ve gotten from a couple winemakers who have been at this longer than I have.
I am in total agreement with the statement that the early (new) oak contact is the strongest. And the percentage of wood to wine contact that exists with a half barrel serves to increase this character.
What I do sometimes is if I have a barrel that is less interesting (more than once-used barrel)…let’s say after a year in barrel…and I have wine being housed by a brand new barrel, I will switch the contents. I have noted a “calming” of the wine that was in new oak, and a “brightening” of the wine that has just been moved to the newer barrel. In the end I am blending the contents of all the barrels (typically 7) for my regular Black Cat bottling, after drawing only some portions of some barrels for my Special Selection. So I am always tasting and thinking of the 2 wine efforts that will become the bottlings of my next vintage.