4 weeks good...8 weeks too long. But in four weeks, you won't make much keepable gains. That's why no one does dbol only cycles, and neither should you...if you're thinking about it.
Dbol with Proviron will harden you up some,Dbol with Liquidex or Armidex has ofter been called "the poor man's Anavar".
Also expect to loose 80 percent of your gains.(Most will be water weight anyway)
RADAR