The other reason is that my credit union pays me 4% interest on up to $20,000 in checking. Why take out good money that could be earning a 4% APY from my bank account to pay early?
Wow! That's an utterly amazing APY! Much better even than most CD and treasury bond rates. Very impressed.
Yeah, actually loss on potential bank account interest due to paying earlier/more often is the only thing that's ever really made me question my system. However, I definitely don't get APY that good, and also tend to prefer investing in the stock market over keeping big chunks of cash in savings. I know I don't meet expert advice of 6-8months emergency liquid savings, but it's just hard for me to justify when there are so many higher yield things I could invest my money in...plus I also just really enjoy investing, so that makes it even more tempting.
Anyway, I figure any interest I'd see over keeping the cash for a few extra weeks is fairly minimal.