I find when I participate in monthly challenges, that's when I do most of my experiments. I really don't doodle small maps on my own as experiments (at least not in 10 years). In fact regarding hand-drawn maps, I tend to avoid letter size and smaller pieces of paper because of the lack of space to draw larger areas, and I find the pen lines too thick at that scale. I prefer hand-drawing to nothing smaller than an 18" x 24" piece of paper, and more often 24" x 36" and larger. Of course, because I have access to large format scanners (42" wide by any reasonable length), drawing on large sheets makes more sense for me.

Really, I trust my hand-drawing skills enough, and my cartography/geology/geography knowledge well enough, that I often experiment on a map intended to be a finished piece as a professional commission or for a map I intend to publish myself. I don't doodle, I generally only work on maps that I intend to be finished and used - not put in some doodle pile.