400km brevet and tour to Hamburg

Since I do not need the Superrandonneur qualification this year I decided to skip the 300km brevet and did a tour to Hamburg on the same date instead.
That was a quite easy tour, I had mild winds supporting me, only a few hills during the beginning and after about 10 hrs and 250km distance I reached Hamburg.
An easy and nice tour.
Two weeks later I started the 400 km brevet in the Weserbergland. The weather was brilliant but a bit windy. I went 280km with a small group, but then I suddenly felt bad and exhausted and decided to take a brief rest.
But I felt worse and decided to slowly proceed the the next control at about 300km and then to rethink further actions. When I reached the control I decided to take a longer break and get a bit of sleep. Afterwards I aboandoned the brevet and returned directly to the finish, skipping a good 50km.
Of course the 50km would have been possible to do and not even the time limit was a matter, but I enjoyed the kind of luxury to just return.
I am undecided yet whether I should start the 600km brevet this year or not.
I am not as trained as last year, maybe the 600km brevet would be a good highlight for this year.