Yeah Dark Horse is like that with all its manga properties. The only exception I can think of to the delayed release rule would probably be the Gantz series which pretty much comes out regularly every other month. If you wanna talk about huge lengths of time between volume release though try reading MPD Psycho or Kurosagi Corpse Delivery Service. There's at least a 2 year gap between each volume release.
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Back from the dead and now 25% less evil wink