First of all, having members of your group play material that they can’t sink their teeth into can be uninspiring, and consequently, can result in a poor performance. This is a drag, not only for the members of your band but the audience members that have paid money to hear you. Secondly, continuing to use someone who's not working out in your group, simply because you’ve already rehearsed them, is harmful to your music and to the person you’ve hired, since they cannot be a positive contributor to the situation. Thirdly, releasing a recording, not because you like it, but because you’ve spent money and time recording it, hurts because, now, you have to devote six months to a year of your life, promoting something you don’t like, instead of creating something different that you do like.
When economists refer to the “opportunity cost” of a resource, they mean the value of the next-highest-valued alternative use of that resource. If, for example, you spend time and money going to a movie, you cannot spend that time at home reading a book, and you cannot spend the money on something else. If your next-best alternative to seeing the movie is reading the book, then the opportunity cost of seeing the movie is the money spent plus the pleasure you forgo by not reading the book.
In more recent times, I find myself weighing the opportunity cost of playing other people's music--especially since what I do is so specific. And this is something that creates a lot of conflict with me. Because on one hand, I like the connection aspect of working with others and it does give me another perspective and a different set of challenges. But the fact of the matter is that this is valuable time I could be developing my own thing. So being a successful and active freelancer does have significant opportunity costs.
Worrying about wasted time, is a waste of time.
It's ALL good!