I may be jumping to a conclusion, but I think SmartThings “never” polls a low-power (ZigBee or Z-Wave) Device (unless a SmartApp schedule or Refresh command is explicitly issued). But I might be wrong.
If my assumption is correct, then it is up to the ZigBee or Z-Wave configuration parameters sent to the Device (or its own defaults) that tells it how often to “wake up” and send a Status, if it feels it has a meaningful update (e.g., a battery level or temperature); and, of course, it wakes up to send a critical Attribute change (e.g., locked, unlocked, tamper).
There isn’t any value to Polling except if: (a) the device’s status updates could be lost from time to time, which is certainly possible, and/or (b) the device’s own wakeup interval is too slow or unreliable (e.g., a device’s battery dies before it can wake and send a final low-battery update… ?
The other variable: What exactly does SmartThing’s optional “Device Health” feature do? Does that add timed Polling? Maybe… Therefore, I’d suggest turning off the Device Health feature and see if that, perhaps, lowers battery drain.