Whether you should use mulch in your garden every year or not depends on the mulch you have applied and how deep it is. When you use new mulch every year in your garden it rewards you with several benefits like weed suppression moisture retention and temperature regulation.
With time mulch decomposes and soon loses its effectiveness. Add a fresh layer of mulch each year to your garden to ensure your plants continue getting these benefits and replenish nutrients in the soil as the old mulch breaks down.