Sue, I'm a working stiff too, and I think they should certainly provide lots of 7-day routes, don't get me wrong. But for us, if we go across the pond, I like to go for at least 3 weeks. My boss doesn't like it much, but I find it not worth it to go for a shorter time. (And it's also better for the environment, although not as good as not flying at all.)
So with a 10-day cruise, we can still manage at least a nice post-cruise or pre-cruise, like we did for WAVE--1 night in Nice, and 6 nights in Portugal. Then again, when we did the 7-day Black Sea, we had a full 6 days in Greece pre, an a full 6 days in Istanbul post, so that's great too.
It's also just the feeling on the ship at the end of a 7-day--it seems so short, and it's always disappointing getting off.