Up until 2 years ago, I would only use the drop position for a period of 5 minutes or less at a time. The pain was immediate and constant, not from the back, but from the crotch. Both saddles on both bikes were the same, it felt like some sort of torture.
After experimenting with different saddles, and extending total reach (top bar length +stem length) I am much more comfortable with it, and now use in over 50% of the time. It is good to have 3 usable positions, and I find I can hold the drop position for one half hour at a time now. It seems more natural, and more stable at speed, and high cadence. Just my two cents!