RE: whats harsher on the liver?
Liver stress/burden/load (or whatever you want to call it) is the amount of drug through the liver per time. So 20mg for 12 weeks will be quite a bit "safer" than 50mg for 6 weeks. Not only is it a lower overall dosage (as the same overall would be 25mg for 12 weeks) but it is taken over a timescale which is double.
A similar example could be shown through alcohol consumption. 21 units per week or whatever the "recommended" safe level is, is best spread throughout the week rather than 'binged' over 1 or 2 days. A more intense example would be using paracetamol. You could feasably take 4*1gram doses for 1 week and suffer no liver effects, but take 56 * 500mg tablets (the same dosage for the week) all at once and you're likely to have a bit of bother