What are some methods to shorten refractory period?

Hi guys, my wife and I I have been together for ten years and have a great sex life but one thing that often bothers me is that I once I become erect and ejaculate, it takes me days to become erect again. Its like all or my arousal exits my penis and there is nothing left. Thankfully we use toys and I can usually make her cum from penis but round two is non-existent. Any idea how to shorten that refractory period?