There's a big difference from giving harsher penalties the more felonies you commit, and giving life for the third. The first is giving the power to the court to give an appropriate sentence, the second is going to be unjustified in many cases. If the offences are bad enough, they'll get life if it's justified.
Some people deserve the chance to change, if they don't they should and will be punished. Drug addict example would be if an addict kicks the habit and sorts their life out.
Sorry don't want to derail this thread so I'll leave it there.