I routinely keep yeast in the fridge for a few weeks up to about 6 weeks at a time in Mason jars or 2000ml flasks.
I keep 1040 wort in mason jars (pressure cooked) in my home office. Usually the night before I brew, I will toss a jar of wort into the fridge (or at least for a few hours). Then before I start heating my strike water I will decant off any clear spent starter and add in the jar of of 1040 wort. Usually by the time I am ready to pitch I have some visible activity in the flask.
If the yeast is any older than 6wks-2months, I will usually start this process about 1-2days before just to make sure all is well.