man ping says:
     -w waitsecs
             Stop ping execution after waitsec seconds. This option is
useful
             when trying to ping unreachable hosts.


However,
for hosts that are down (and therefore don't respond) this option does NOT
work. ping will wait indefinately untill the user kills ping.

The wait option therefore becomes rather unusefull.

note: The host MUST be a valid host with a valid route, etc, and would
normally reply correctly if it were up and running.

best way to verify:
ping a host (ping -w 4 <ip>) and notice it'll stop after 4 sec's.
pull the plug on that host.
ping the host again, and notice ping won't stop after 4 sec's (it won't
ever stop).