Yes...you should refrigerate them. If you're going to this much effort to save your slurry, you should consider attempting to harvest yeast and save it in either plate or slant form. Less than $100 will get you all the kit you need to become a proper yeast rancher.
To reenergieze your slurry, simply make a 1000 ml starter 3 days prior to when you want to use your yeast.
Planned: American Wit
Secondary: Abbeyish Ale