I've had knee problems in the past and my knees feel better with fuller extension. I have noticed that at the extreme high end of adjustment, (which is where I like to ride) small distances matter a lot. When I switch seasons (shoe sole thickness--Chucks vs hiking boots, for instance) I'll fasten my back reflector almost at the seat post locking collar (like 1/4" or a bit farther away) so that I can make quick small adjustments with that distance as a reference for easy visual measurement and by the time I've gone a block or two I'll have it dialed in. I think as you do more of it you will learn what you like and it will be easier to get it right quickly.