For my summer round (late June) I started biulding up the climbing in Jan and reached 10,000 in early march. From there on i did 10-15,000 most weeks, with the odd week of doing a little less to rest and a few more bigger weeks during May (inc the Fellsman). This seemed to work.
For winter, I had a better starting base of fitness so went straight into 10,000+ in early august for a mid-december round. I averaged 14,000' a week from august to dec, but i was not working and could fit more in.
So, about four months of 10,000' a week plus climbing for me in both cases.
Whilst the amount of climbing increased slightly throughout these periods, the proportion done on the 'big day' in each week went up. the emphasis changed from lots of outings of 1500-3500' to big days of 8000' plus, with more rest days. I think this helps prepare your fitness and your head.