Ride or replace?

Replace but keep it after a patch up. Bond a normal tube repair patch on the inside and then super glue the tear together.

Hang in the bike store as an emergency back up (only to be used if you get a major tyre failure and need to use the bike). Use a puncture repair crayon to mark the tyre as emergency use only. 

Also, don't throw tyres away. A couple of them taped together provide great frame protection when transporting your bike. Particularly good if you transport your bike with club mates in a van or for padding out a bike box.

Murphys law say it will fail in the most inconvenient and unpleasant situation. Warm house at leisure is recommended

Depends on how much risk you want to take and how much you enjoy repairing punctures by the roadside in winter.  I was cycling down lanes to work yesterday in the apocalyptic aftermath of Storm Barney (or whatever it was called) thinking the last thing I needed was a puncture.  Personally, I'd replace the tyre.  Someone else might have some advice on a 'trick' to patch the hole up a bit.