I love both looks. The grey skirt look is particularly great. Really love that little kick pleat detail on the skirt. I am trying not to buy winter skirts (since I don't wear the ones I have enough), but I am really tempted!
Re: the boots. The new ones are amazing and I agree the old ones are not so exciting next to them. I guess I would base the decision on whether to keep on comfort. If they are super comfortable, I would keep them for days with a lot of walking, or bad weather, or whatever. But I often find that when shoes get old, they wear down in hidden places and become less comfortable.
If it helps, I literally just took a pair of boots to the cobbler today to get the heels replaced. I know it's time when my heels get so unbalanced I start feeling like I'm going to trip all the time. It cost me $25. I find that the replacement heels often last longer because they are better quality, and you can ask for the ones with more traction too.
ETA: In my experience, I usually get my boots reheeled once but once the heels wear down a second time, there are usually too many other things wrong with the shoe that are not fixable/extremely expensive to fix.