I don't know about all that "units" stuff, but I know that it's not so much because of the label as to why albums are so short as it is because of how much the composer is willing to pay for the length of their albums. I have plenty of scores from other labels like Decca (X-Men score is only 40 minutes) and Hollywood records (Hildago is 45 minutes) or the Congo score from Epic Soundtrax which is 33 minutes long. James Horner's scores for Varese Sarabande are very long. Orchestral scores are expensive, yet if a composer does the entire score with a synthesizer for Varese (or any label), it's cheaper, and therefore, longer. So the "union" thing definitely comes into play (I even emailed Marco Beltrami once and he explained it to me), but i'm not sure if the certain number of units factors in.