Some worry when you get a "grey" water on top. It's just the alcohol the culture produces when feeding on the goodies you put in every couple of weeks. I have had no issues going three weeks, after that you are in uncharted territory as far as I'm concerned. I use bread flour to feed mine, might use whole wheat if I'm gonna make a whole wheat loaf in the near future. I think the whole wheat has more goodies that get it cranking pretty good, even in the fridge.I like a sourdough with good tang so I will have to experiment with the ranges.
When is it too late? I have made starters in the past and let them go WAY too far after not getting great results. They have been a pain to start so I would like to make sure I know my outer limit to keep this healthy. Is 2 weeks pushing the time spent in the fridge, or if I got distracted for a week could I bring it back easily?
One thing, check the temp where you put it in the fridge. I have mine up top where it runs in the high 30s, in the bottom it runs in the very low 30s. The colder it's environment, the longer it can last between feedings. That's why you can do 2 weeks in the fridge, but need to do it more often in ambient kitchen temps, but in the great white north where you are, you can probably go longer than 4 days outside the fridge.