When I was backpacking, I entered Germany without a definite exit date and with no onward travel booked. Upon hearing this, the immigration official gave me a hard stare, and let me sweat for what felt like ages. He then cracked a smile and told me to visit the Foreigners Office if I wanted to stay for longer, or look for work. While I doubt that's the normal experience, including finding an immigration official with a sense of humour, I found Germany to be pretty flexible in this regard.