Look at you go 80+, especially considering the speed limit is 65 here. I got a speeding ticket the other day and while the cop said I was going 80+ he knocked it down to 79. Mine is not the Master's collection though, it was the Bastard's collection (me being said bastard, but I digress).
So in honour of this mercy, I shall call you 79. You don't mind me calling you 79 do you? Cause this art you're doing is obviously making you younger and younger.
I'm very impressed by your sketches. And some are a wee bit stronger than others I think, as always seems to be the case with sketches, but they are overall holding a respectable level. You've got a good chronicle of where your eye goes.
One thing that you seem to be doing is looking for the portrait resemblance somewhat which is great. It's also kinda cool if you show it to the individuals. They're flattered and it's an open door if people then wish to speak to you or visa-versa. My dad was of the kind who would speak to everybody, but he wasn't an artist. Me, on the other hand, I never really showed my sketches to the subject. I was more private that way. Just thinking aloud here.
But I would suggest a couple other things to look at:
1) you may want to begin thinking in terms of paintings. And should you want to, you may want to also use sketching as a way to open up your canvas strategy, setting your light and dark pattern and how the eye moves around the canvas, especially when you get into the more full figure studies. It'll help you when you go to painting.
2) You may also consider developing a formula for how you approach a head or a figure. I'm not saying you haven't got a loose formula, but it's never a bad thing to consider what marks and nature of marks best describe a head and figure. I think the advantage to this is that you can seriously improve on your images by making them work as your own rather than being held accountable for each little thing that you are looking at. You're not a camera after all.
Anyway, aside from those comments, the energy of your work is awesome and you are really looking well and getting to where you can get it down on (virtual) paper very well indeed. Well done you!
"Not a bit is wasted and the best is yet to come. . ." -- remembered from a dream