Prior to Splunk v7, Splunk was on version-based EOL. We supported based on current major release and 1 prior major release. For example, if we have Splunk v5, v6 and v7, v5 reaches EOL and the current v7 and 1 prior v6 is supported.With Splunk v7, Splunk has moved from version-based EOL to time-based EOL where a major or minor release is supported for 24 months.
For example, Splunk v7 was released on September 26th, 2017 so it is supported until September 26th, 2019 which is 24 months since its GA. If 7.1.0 is released today, it will reach EOL 24 months from today.