Better to keep it permanently in your backpack/pannier and never take it out (except for use at work). I have a can of deodorant I use like that. It just saves me having to go into the office itself and rummage around for it. Of course, that's only a problem if, like me, your desk isn't as clean as it should be.

20 degrees C this morning. So much for "winter". Reasonably sane ride in, except for one bus driver who made a couple of pathetic attempts to cut me off. I soon dropped him pointlessly in the gridlock near Sorrento shops, so it didn't bother me too much. I saw Halley's comet six times this morning while waiting for the set of lights at the intersection of Ferry Road and Cotlew Street to change.