I have 5 raised veggie garden beds - about 200 square feet. I use cypress mulch. I always read-mulch, mulch, mulch. My question is can you use mulch again from one planting, one one season to the next? Or should it all be removed and use new mulch? Am I causing problems by reusing it?

Reuse it until it starts to break down and become part of the soil structure, then put on more. I put on fresh mulch every season, and if I do a lot of planting mid-season I may need to add add'l mulch around the plants.