What should we do with Sex Offenders?

I think we should keep them in prison a lot longer then what we have been doing. We let them out within a couple years and they are back on the streets doing what they do, being sex offenders. People who get caught with drugs are put in jail a lot longer then sex offenders which to me is wrong. They both should be put in prison for a reasonable amount of time. That way they are off the streets and in a place where they can't harm anyone and are able to take time to think about what they have done.