Jack, I was using cofocus as a cross as well. I had some laying around so i tried it as a main in an OGSM hybrid. I have to say I was rather impressed coming from the springy Cyclone/Nvy setup I had before. the control level was much higher, but the comfort level took a surprising hit.
6 hours in the cofocus was completely dead (18x20 pattern)
What I learned from this was basically to try some of these out as a main first to see how long they last. It gives you a better idea since it is tougher to tell in a cross with gut.
I think 4g is the best cross you could get (if you can afford it). It lasts WAY longer (10-14 hours of play which is about 2 weeks for me). If you can't afford it, I would go with Black Magic. The feel of BM with gut is simply awesome.
It sounds like you may have already found a cross that works, so maybe just disregard everything I just said..lol.