A very tired cyclist.

It's spring - yeah, for the first time in months I am in shorts (not a pretty sight), it feels great. Feeling the suns warmth on your skin, it's like feeling well after a sickness.
I've been forcing myself to do really long rides of 200kms, There is a 400km event in october that I have to do to pre-qualify for the Paris / Brest / Paris. The actual qualifiers start in November, but if you do a distance event before then, it means you have more chance of not being turned down due to too many entering the event. How do you go from a 200km ride  to a 400km ride in one month? I find 200kms demanding enough. I am trying to do a 250km next week and then a 270km two weeks later, in the hopes that the 400km can be broken down into a 270km with a rest, and then finish the remaining 130km.
I'm finding this all very demanding, I still don't know if I can do it, but part of it must be mind over matter and I know how to be determined, and I know how to suffer. Will that get me through?
I've been training myself to drink coffee for the caffeine hit, I much prefer Tea, but I need more caffeine to stay awake and alert.
In the meantime the sun is shining and it is blessedly warm. We just need those daylight hours to extent so that I don't have to go through so many batteries with the night riding.