The stuff I mentioned can be bought in 5kg bags which will last you a month at least - depending on how much meals you're replacing - if it's all then you'll probably go trough more - you can pre-mix a week worth in a standard plastic container and shake in like two minutes.
The major time difference is going to be in figuring out how to do it the first time - but this is time well spent if you want to balance your nutrition (figuring out how much protein/fat/carbs you want and how many calories).
I'm in the same boat - I don't want to cook every day or eat out all the time - this is convenient and works towards my fitness goals. Throw in a multi vitamin, fish oil and some fruit/vegetables and you got a easy to do fast and cheap diet for building muscle.
As I went vegan I went from benching 120 to 200 with about 20% protein intake, and it was fine. We don't need shit tons of protein that everyone says we do, Soylent has a nice ratio of it.
20% calories from protein is fine. Even for a strength athlete, if you are trying to gain muscle mass, 20kcal/lb and 1g protein/lb is a reasonable set of macros, which indeed is 20% calories from protein. A lot of bodybuilders will go up to 25% or even 30% from protein, but that's on the high end and certainly not something that would make sense for non-strength athletes.
