In reply to Si Cox:
> I can go up to five times a week, for a maximum of 35 minutes per session, although try to break it up with a run per week. Generally looking at four sessions a week.
> Currently, I am doing a lot of traversing on increasingly steep gradients to build up my strength, endurance and footwork. I then try and work a few problems, focussing on areas I feel I am weak (e.g., slopers or overhangs).
I've found that lots of short sessions in a week can be really worthwhile - you don't have time to get completely trashed, so you'll be well recovered by the next session. If you look at the whole week then you end up with almost two and a half hours of high quality training time, compared to one long session where you take your time warming up, waste time and eventually get tired.
When I've done "little and often" I haven't tried to do too much per session - it's easiest to concentrate on short (3 or 4 move) problems to work max strength/power as it takes less planning and organisation: you just turn up, warm up for 10 minutes then have a few goes on hard things. It's possible to do more endurance stuff, but it takes more planning. You can spend a couple of sessions preparing - working out a longer circuit, getting the moves wired, experimenting with rest positions - then the final couple of sessions in the week can be used to do pyramids of repeats of the circuit without wasting time thinking about what you're going to do.
I don't think you can really train for full stamina in 35 minute sessions, they're just too short to do a large enough volume of easier climbing, but if you can arrange fewer but longer wall visits every few weeks then it can be fitted in.
Technique/footwork can be trained during the endurance/stamina weeks by concentrating on climbing as well as possible, even (especially) when completely boxed.
So in summary I'd say that you could make better use of the time by seperating out power/endurance/stamina and concentrating on one area.