Last year I overwintered my geraniums, by putting them in brown bags and storing in the basement.
I can’t remember when I took them out of pots & the ground.
Should I take them out now while they are still blooming?
Usually the plant signals when it is starting to struggle with cooler weather and low light. Certainly you want to bring them in before frost. As long as you are enjoying the blooms, leave them outside. An fyi: there are 2 very different types of plants often called geranium. I am assuming you are talking about "zonal geranium" or Pelargonium to differentiate it from the genus Geranium.