http://www.cboe.com/products/stock-...ons-with-a-m-settlement-spx/spx-options-specs
=============== Expiration Months:
Up to twelve (12) near-term months. In addition, the Exchange may list up to ten (10) SPX LEAPS® expiration months that expire from 12 to 60 months from the date of issuance.
===============
(didn't see more detailed info but you can actually contact CBOE, they're often responsive)