The exact WLAN range of the Tobii Pro Glasses 2 depends on the hardware you use and in which environment you are using it.
Outside of buildings and in environments with low radio pollution you will have a bigger WLAN range than inside of buildings and in environments with high radio pollution.
In case the Tobii Pro Glasses 2 went out of range it will disconnect from the PC/tablet. However it connects automatically when it gets back in range again when the Windows feature for automatic re-connect is enabled. To enable the automatic re-connect feature make sure you select the option "connect automatically" when configuring the WLAN connection the first time. In case you already configured a connection for the Tobii Pro Glasses 2 you can disconnect from a previous WLAN network and let Windows "forget" the WLAN settings. Then connect the Glasses 2 via WLAN and choose "connect automatically".