Like Brandon, cross is my main focus for the year in competitive terms. I do 'train' for running in races, mainly through a weekly 1-2 hour 'technical' session which will include practice dismounts/mounts, shouldering the bike, bunny hopping and running short, steep ascents similar to those found on an average course. If I am aware of any specific technical sections on a course that I am racing on the next weekend then I will weight the sessions in favour of these. These sessions are usually with a 5+ guys that I race against so they can get quite competitive! Or they might end up at the local pub if it's too cold/wet
In addition, I do one pure running session per week of just over one hour, 5-10 minute gentle warm up, then about 45 minute fartlek session comprising 10 x short hill climbs on sand dunes with 5 minute recovery between sets, then 10-20 minute gentle run home as warm down.
During the season, I'm probably riding intervals and recovery rides only for total of 6-8 hours including the above then race on Saturday and/or Sunday.
Cross is mostly zone 4-6 training and speed orientated during the season hence the low hours spent in the saddle. This makes sense given the lousy conditions we're riding in most of the time and the increased risk of running yourself down and picking up infections at that time of year. I've spent very little time in the saddle since the end of January and have just started level 1-2 rides of 3 hours to kick off next seasons training.
Can't vouch for other crossers but this seems to work for me. Hope this helps