This is a very good question. When we were running on version 8.2, we had it turned off. We upgraded to 9.1 last October and ever since have had cache issues that still have yet to be resolved by Sitefinity. We were told to remove the "false" setting on the L2 cache and all would be good. However, that contradicts with everything they have said in the past. We did do it and it did help somewhat. we still experiment with intermittent cache issues all the time, which is unresolved iwth Sitefinity support. The ticket has been open for a very, very long time.
Best of luck. If you find any resolution that resolves the caching 100%, please feel free to share.