I've never really timed myself, but I kinda enjoy changing strings.For length on the tuner,I use my middle finger at the 12th fret as a guide, holding the string with my thumb.I then thread the end through the peg until fairly tight. Then I wrap the string backwards around the peg,come up under where the strings enters and pull up the end. At that point I wind the string until it is tight,tune to pitch, and the pull on the string to stretch it.Retune, stretch again.When all the strings are on, I pull to stretch and retune again.
It really doesn't take that long and the backwards wrap at the peg serves to lock the string under itself, stopping any slippage.
It may be a function of my particular guitar and the strings I use,D'Aquisto Brass Masters, but my guitar says in tune for long periods of time.So much so that I can carry it in the case to a campsite session, pull it out, and be in tune with those already playing.
Assuming,of course,that they are in the proper state of tune to begin with.Sometimes it takes a couple shots of single-malt tuning fluid to get it there.