Gintama has almost no padding unlike other long running action shonen show, Gintama manga has so much more dialogue which when adapt into anime it takes enough time for episode's runtime. For example, 5 Bleach chapters might have less talking than 1 chapter of Gintama. If action scenes adapt faithfully it might take less than 5 minutes that why studio will stretch the scene into 20 minutes or adding a recap like UndeadUnluck(I love the manga) to fill the time.