Most types of insulation should last for at least 20 years, and in many cases they will last for much longer than this. Many varieties of attic insulation, for example, should last for at least 40 years. The only time it normally needs to be replaced is if it has been compacted by someone standing on it.
For cavity wall insulation, installations completed by registered professional installers are normally guaranteed 25 years. The chances are that cavity wall insulation should actually last a lifetime.