I agree with Gary. Excellent overall physical conditioning will go a long way. Plus it is usually a lot more interesting than jugging a rope. I've spent some time thinking about expedition training. Just waiting for an expedition to come along for me to use it
Anyway, if I had a few months to train for a big trip my theoretical breakdown goes something like this.
3 days aerobic conditioning: Running, biking, jump rope, anything. I find trail running to be a better specific training for caving as it forces you to be a little more vigilant about where you place your feet, much as you have to be when caving. Plus running on pavement bores the hell out of me and hurts my knees. And biking on trails is also, well, just fun. It's important to have fun.
2 days strength training: Lift weights if you want, but I also find this boring. I find workouts where you just use your body weight to be more appropriate. After all, you're not trying to bulk up! Pilates, yoga, rock climbing, etc. Spend these days also focusing on stretching a LOT.
1 day specific rope training: Jug that rope, do rebelays, changeovers, etc. untill being blindfolded doesn't slow you down at all.
1 day of rest.
Another word of advice as far as training goes. Not caving related really, but just as far as training for anything specific. Most people jump in whole hog and do really well at first until they get lazy or injured. Depending on your base line fitness, jumping into workouts 5-6 days a week might not be the best idea. You don't want to get injured and miss out on the trip you're training for. Start 3 days a week if you need to. Whatever you have to do to stay healthy. And also take the week ahead of your trip off from training. Get rested, maintain your stretching routine and eat well.