Performance impact of turning up Max transparency bounces? When using transparent objects, if you do not allow enough transparency bounces (set in Light Paths) then you will get black artifacts. Having more transparent surfaces and bounces slows down the render. But does it matter if your Max bounces area higher than the number of surfaces in your file? If you have 0 transparent shaders present and turn Max bounces up, does it matter? Is there any reason not to always leave it at a high number?
No, it has no effect if you do not have any transparent shaders in your scene. Setting it too high could result in a lot of extra bounces being calculated for little result on some stray transparent object. One of those corner cases that comes up sometimes. Additionally, some would say the default of 8 (with no early path termination, since the minimum is also 8) is already a "high" number. It depends on your scene and your goals. Adjust accordingly.