If you are still running VMware vSphere 5.5 and vSAN 5.5, the End of General Support (EoGS) date is September 19, 2018. vSphere 5.5 was originally released in September 22, 2013.
There is however an extended support option until September 19, 2020. For more information click on this VMware Extended Support article. Be aware that VMware will not provide any additional patches and/or bug fixes.
Additional EoGS products for September 19, 2018:
We suggest that you start planning your upgrade to vSphere 6.5 or 6.7. As your knowledge leader when it comes to designing a multi-site, high-availability virtual environment, our Team is always on hand to answer any queries and help you with your migration plan.
For additional assistance with this and other VMware questions please contact Helient at service@helient.com.