Should a prisoner serve the full term they a sentenced to?

Yes and life should mean life. I heard of a case where the person got 3 life sentences and only served 7 years, that can never be right. How do victims feel when they see this happening?. If prisons are overcrowded then build more instead of giving all these expenses to MPs. I am sure the tax payer would prefer to see their money spent on something worthwhile such as more prisons.