Does a vsan license last a lifetime or does it require a yearly fee? Is it transferable to a host if say one is retired and a new host is commissioned?
The license for VSAN have no expiration. You may have a date limit for support subscription (SnS) from 1 to 3 years,but you can renew it.
As the license is purchased per processor (or per VM in case of a VDI deployment) you can have as much ESX servers in a cluster your license supports, does not matter what hosts are these - so yes, you can use the license code in any hosts,never having more CPUs on the cluster than the VSAN CPU count have.
You can assign a valid license before evolution period (60days) expired and subscribe for 1 to 3yrs.
Licensing for Virtual SAN
When you enable Virtual SAN on a cluster, you must assign the cluster an appropriate Virtual SAN license before its 60-day evaluation period expires.
Just like vSphere licenses, Virtual SAN licenses have per CPU capacity. When you assign a Virtual SAN license to a cluster, the amount of license capacity that is used equals the total number of CPUs in the hosts that participate in the cluster. For example, if you have a Virtual SAN cluster that contains 4 hosts with 8 CPUs each, you need to assign the cluster a Virtual SAN license with a minimum capacity of 32 CPUs.
The license usage of the Virtual SAN cluster is recalculated and updated in the following situations:
You must maintain the Virtual SAN clusters in compliance with the Virtual SAN licensing model. The total number of CPUs of all hosts in the cluster must not exceed the capacity of the Virtual SAN license that is assigned to the cluster.
Hence cost based on subscription duration so not for a lifetime you have renew it accordingly.
VSAN licensing is perpetual unless you are the 1% of VMware users who are in the vCAN program (service providers, kind of like VSPP) or if purchased as part of EVO:RAIL (EVO:RAIL is OEM licensing and dies with the device).
If you want free updates, you will need to keep your S&S current. If you bought it today, and deployed it you could keep using it (without support or upgrades) as long as you wanted.
VSAN License requirements:
For vSphere 5.5