thats not really a "rule"

its dependent on the oral itself and the dose. heck you can run VAR for a year straight !! VAR is prescribed to treat alcoholic liver disease, so NO its not bad on the liver, it helps regenerate it. thats why I find it crazy when guys tell girls who take VAR to take liver support with it (even though their dose is so low the same as a prescribed liver patient dose), LOL. its all 'cookie cutter bro science' being spread out there.
now back to the Dbol.. your really only taking a mild normal dose for the first 4 weeks. your tapering things down over time and thats why you can run it so long and you should run it long. 20mg of Dbol is no harder on your liver then one beer a day. big deal.... sure run TUDCA and NAC, heck I even do that when off cycle. my point is that a 10 week taper of Dbol is way more effective and has less sides then a stupid 4 week blast of Dbol.. the taper method is tried and true. the 4 week blasts is what gives Dbol a bad name from newbs that don't know what they are doing and say they lost all their gains and only got bloated from dbol