Hi all,
I have configured z-wave switch in Vera and receiving its key pressed status into openhab via mios binding, it works perfect and very responsive but if i leave the switch for few hrs then the first press takes almost 4-5 seconds to get response back into openhab.
could this be a configuration in mios binding or could it be zwave configuration for device in vera ? wakeup interval may be ? - any pointers will be helpful 
When you activate it, after leaving it for a few hours, does Vera see the response instantly?
In general, the MiOS Binding should be as responsive as any of the Vera control points - since it’s using the same mechanism they do to sync changes to the data.
If you open a standard MiOS Control Point, or the Vera UI, you should see a similar rate of change when devices are manually activated.
For ZWave Devices that don’t support HAIL (Instant Status), you may also have to wait for MiOS to poll the device before notifications occur on manual-activations. I have Leviton VR-series switches throughout my house, so it’s generally not a problem, but even then there are times that Vera isn’t instantly in sync with manual changes.
The only other time I’ve observed delays was when I first started using openHAB (on a RPi B+). At that time, I had way too much logging enabled, and the device itself was underpowered (memory + CPU) so certain actions would lag considerably.