The Department for Communities said it would make the change this spring, to mirror existing legislation in the rest of the UK. It means up to 7,500 pensioners in Northern Ireland will now not have their PIP regularly reviewed.
"This is welcome news and will come as a relief to thousands of people who have to claim this benefit," said Mr Lunn.
"However, this does not change our concerns about PIP, which we have continually raised, and how it is administered, particularly with mitigation measures due to end next year. There is no doubt the system is creating stress and pressure upon people, with no consideration of individuals' particular circumstances or the impact PIP will have upon them.