If you can hit your protein goals (as given to you by your surgical team), without the drinks, there's no real reason to continue them. If, on the other hand, you need the extra protein from the drinks to hit your goals, there's nothing wrong with using them indefinitely. Said differently, there is no specific time when you need to "give them up" post surgery. I'm over two years out and still use them. That said, I'm also shooting for 150g of protein per day, which I just can't get close to without some whey protein or a fairlife drink.
If you find the premade shakes to be prohibitively expensive, you could always get powdered whey protein isolate. That's generally considered the highest quality protein powder. Other even cheaper protein powders are available, such as whey protein concentrate, but those will have more fat and lactose.
I think in terms of grams of protein per dollar, it would be hard to find things as cheap as powdered whey protein. Beans would probably be about the only thing I can think of, though it's hard for most of us to eat a ton of beans since while they are protein rich, beans are not particularly protein dense. Most all meat is generally a lot more expensive than whey on a gram for gram dasis. At one time, I might have put eggs in the less expensive category, but I'm not so sure anymore without running the numbers.