Is there any reason *not* to enable 802.3az (Energy-Efficient Ethernet) on a switch?

From the user guide of the product:

An EEE-enabled device initiates Low Power Idle (LPI) signals to negotiate and wake up the remote device when there is data to be transmitted. To use EEE, both devices should be EEE compliant.

EEE is configured on a per-system basis in the Switch. If one of the networking devices that connect to the Switch doesn't support EEE, EEE may not work in the Switch to save power.

Press in the IEEE 802.3az EEE ON/OFF button on the front panel to turn on the EEE feature. Disable it if you don't want the network performance to be impacted due to the latency from the additional time required for the sleep and wake transition or if the remote side doesn't support it.

This basically says that if one device connected to the switch does not support 802.3az then the power saving function might not work, hard to tell so just try it. But it does lead to a slight latency so if that is an issue then turn off the energy saving function.

In my case [router does not support it, laptop does], the connection kept on dropping and reconnecting very quickly (within a couple of seconds). I had to disable Energy-Efficient Ethernet to get a functional connection.

There are some usages, that need EEE disabled. For example Dante audio networking will not work with energetically efficient switches.