Drysuits are only dry when the gaskets and zippers are undamaged and working properly. Latex gaskets will probably eventually need replacing, but you can easily repair them yourself.
On the other hand, replacing a drysuit zipper is definitely not DIY, and it’s a very expensive repair. Preventative care, such as regularly cleaning and lubricating zipper teeth, will help preserve zipper health. Also, using good techniques to roll and fold the drysuit for transportation to and from the water will help prevent fatal damage.
In this video, NRS Repairs guru Josh Gile goes over all the tips for ensuring that the zipper will last the life of your drysuit.