With all that training why do they want experienced controllers? With 5 months in the classroom, including two months in the sim, then 5-6 months OJT I could train a keen student straight off the street.
In addition to what my German colleagues have already stated, DFS is faced with the problem that they don't get enough applications by ab initio trainees. I don't know exact figures but say you need 10000 applications to actually find 100 suitable candidates, and you only get 5000 applications in the first place, then you need 50 ready entries to make up for that deficit.
From what I hear DFS needs about 300 additional controllers over the next couple of years.