Banana bread in smaller pans

I would just make muffin tops with the batter. They are very good, freeze well and reheat in the toaster in a flash.

My answer is less scientific, and more intuition:
If 2 large loaves take 40 - 50 minutes, 3 smaller loaves might take around 20 - 30 minutes. I always set at least two timers - one to check in on what's going on in the oven, the other near when it's close. Even if I know a cake takes 40 minutes to bake, I set my first timer for 20m.

Also, not all baking vessels or batters are created equal. A lot of loaf cakes get overcooked on the outside before the interior is fully baked. Ninety percent of the time this is because the vessel is too full and the batter domes, but then has no wear to go but out, or sinking, or overbaking. If I don't know how much a batter is going to rise, I never fill more than 1/2 way up the baking vessel.

Lastly - banana cake and muffin batter will last at least 3 days in your fridge while you wait for another baking vessel to become free.

An 8x4x2 loaf pan holds 4 cups batter and a 9x5x3 holds 8 cups so you might need 4 of the smaller pans, Check the bread at 30 min