It isn’t always necessary to fully replace the existing mulch. Replenishing the material may often be sufficient.
Old mulch can bunch up so before applying new mulch, rake the old mulch so it is even along the landscape. Apply the new mulch on top. Replenishing can be done every one to two years, providing untold benefits to your plants. This also allows the old mulch to add any remaining nutrients to the ground, as well as save you the time and effort of removing the old mulch.