[professoretc]

> I agree with it only in principle; it seems ripe for injustice in all practical details.

Yep, instead of "you definitely get out of prison after X years have passed" you instead get "you get out of prison in 21 years! (or never, depending on how we feel)".

[lapetitejort]

Per the wiki page, the five year extensions are for the indeterminate penalty, not for any prison sentence. The alternate to this sentence is "We will kill you in prison" or "You will die in prison".