I agree with everyone else here. Very poor design to require the passcode as soon as I hit the lock button when I have Fingerprint turned on. I always hit the lock button before setting my phone down or putting it in my pocket so I don't burn battery or perform unwanted phone actions, and I almost always pick it right back up within 10 seconds to do something else.
Please rethink, Apple! The fingerprint tech is still imperfect (I often have to scan several times), so typing my passcode and/or scanning my thumb every time I do this has made my 5s slower than my previous iPhone.