What happens if I set cacheable=”true” on a block but don’t specify cache_lifetime?

Studying up for M2 cert. Ran into an interesting scenario regarding block caching. Please let me know if my assumptions are in line with reality:

  • blocks are not cacheable by default at the block cache level, but are FPC cacheable by default
  • setting cacheable=”false” on a block disables full page cache for the whole page, as well as block caching
  • passing an argument for cache_lifetime to a block makes it cacheable at the block cache level

So what happens if I set cacheable=”true” for the block, but don’t specify an argument for cache_lifetime?

I’ll probably just create a block and test this by digging through ./var/cache/ but figured somebody might know off the top of their head.