2011/3/1 Philipp Stephani <st_philipp@yahoo.de>

> Yes, in this particular case I would like not to break them.

I don't know whether that still works in ConTeXt, but try
\interlinepenalty=10000

That made havoc of my document.

> What would also be acceptable is when there are at least five lines on the page.

Try this (again untested):
\clubpenalties 5 10000 10000 10000 10000 10000
\widowpenalties 5 10000 10000 10000 10000 10000

Does not seem to have any effect.