RefreshMaxAge generates an event for all active items in the group that have not changed their values for the duration of the passed MSecs (milliseconds) to renew their values.
The values are returned via the OnDatachange event. A MSecs value of 0 is equivalent to OPC_DS_DEVICE, which means that all items are read from the underlying device. A MSecs value of 0xFFFFFFFF is equivalent to OPC_DS_CACHE which means that all items are read from the cache. If no cache exists, the items will always be read from the underlying device.