For the most part, It's been years since I've maintained and used any starters but will answer what I can based on what I remember.
Keep in mind there are many different methods of maintaining a poolish or starter but these are my own personal preferences.
-once you replenish the poolish, place it in the fridge right away. If you forget, and leave it out a while just put it back in the fridge as soon as you can.
-once you take it out of the fridge, I like to let it warm up to room temp before using. I like to use a poolish when it is at the height of its peak or even starting to collapse a bit. If the poolish has already risen and collapse, you can still use it at this point. Being that it is a CY poolish it shouldn't sour on you. If it was a natural starter, and it has collapsed, I would discard half, refeed, and wait for it to peak again to use.
-I don't recall exactly how long it will take a dough with 2% poolish or starter to double at room temperature but I would expect it take around 18 hours? That's a complete guess on my part. Craig has a sour dough starter prediction time chart around here somewhere.
-after maintaining your CY poolish for months, it shouldn't change flavors but I think it is fair to say that ongoing maintenance of such a poolish is prone to contamination or other yeast or bacteria to develop changing the flavor of the original poolish.