Very relevant concepts & a good discussion.
I return to basics here--the enemy of rational thought is all-or-none thinking. Balance time & money. OK to buy full price and OK to watch for sales, all in the same person. Also, I think there is more than one question in your question. Time vs. money, but also focus--if you know what you like and what tends to fit you and you will wear AND you know where to find it, you may save both time and money by buying those things rather than random sale items.
Thrift stores fall into a so-so category for me because it is more needle-in-haystack and therefore a whole lot of time for little return. I'm not a big e-bay shopper so miss that advantage, but it's an example of how one can search for specific items. Might not be there, but is not completely random.
Sale items is a lot larger concept than thrifting alone or even the idea of, it it's not worth full price it's not worth it. It depends on how one is building a wardrobe. With wardrobe & shopping goals & focus, then maybe one idea is, I would like to add a gray cashmere V-neck sweater to my wardrobe, but it's not an emergency, so I'll look after January. This concept works best for classic items & basics.
Or finding a designer jacket that would fit your style but saying, it's okay if I get this this year or not, but I'll put it in wish list and see if it goes on sale. That is more like PPP and not going to after-holiday sales and buying something just because it's on sale.
Your time & money idea would be at one extreme if the goal is, every minute/hour spent shopping must result in a purchase or it's wasted time. That isn't realistic because again, if taken to extreme, you'd force yourself to buy something just because you had invested some time. What I hear you saying is you need a greater % return on your time and that is strategic, but has a range of how it can play out.
Two things I'm doing more of that relate to the time & effort and $ balance are:
I think I need to buy more in-season or pre-season and not as much after season. That may mean more full-price. The reason is because I'm getting burned on being either more fickle myself, if something can't be used for 6 months, or I feel the classics aren't as classic. I'm more about buying a great summer blazer at the start of summer when I can play and remix and wear it, and not in December. Still balance is needed. I just bought a linen-y look , silky-feeling 100% wool T. Tahari jacket on sale because I really loved the fit and fabric, and hope it will still be what I want next spring and summer. It was 60% off and I don't think I would have bought it at full price.
Second, my sizes seem to sell out and so if something is really great I do have to think about whether to plunge or wait. You may be saying as well, that you want to get what you want--"want' being interpreted in its best way, an item that will really be useful. That may mean you have to buy it when you first see it.
