The X1 Search license itself grants perpetual use of the version you purchase.
X1 Search Premium Support is an annual (optional) subscription. Support allows you to access our support portal, submit and track tickets for technical support, and to updates of any new versions of the X1 client released that year.
When purchased with your X1 Search license, Premium Support is offered at a discounted price. If you opt to purchase your X1 Search license without support, you will receive 90 days of free support during which you will have access to technical support and updates of any new versions released.
Once that 90-day window has passed you will need to purchase support in order to upgrade to any newer versions released, which you can do by logging into the X1 Support Portal, here: www.x1.com/support/x1_search.html#login