I got some cheap snap-on fenders last fall. Didn't go back far enough, and flopped around. Backpack got dirty.
Got a rack and panniers a month or so ago. Extended the platform with cardboard and a coat hanger. It keeps my back clean, but the frame, brakes, rack, and front derailer get full of sand and salt.
Got a full fender set this week. Still trying to fit them. Looking forward to easier cleaning.