I'd love to answer your question clearly, that is, with a definitive answer of some kind or other. The difficulty lies in my uncertainty around the whole notion of imprisonment. However I'm guessing you would like some answer based on the reality of imprisonment as it stands.
In that light, therefore, let me say if 'life imprisonment' means the rest of your life, then certainly it should mean that. Otherwise there is but confusion in society and those who have to face that kind of punishment, probably in advance know, if on committing a crime, that they won't have to serve the full term, but only a portion of it. That can't be a strong deterrent, though I doubt that those who have criminal actions on their minds think in terms of being deterred. Enough for now. Thanks for the question.