Yeah, it comes down to the limits of your personal patience and how much time you have to plug away at it, I guess.
Your personal limits seem quite reasonable. It’s rare these days that I struggle with the second level – it’s usually challenging but not enough to make me fail it multiple times.
With the third level of a DC, usually I can at least get to the final room and assess the difficulty of defeating the boss. If it’s one of the many hated bosses I’ve listed in another thread, I probably won’t bother if I don’t get him on the first try, unless the previous rooms are lenient enough to let me get there with a lot of birds leftover for experimentation. If it’s stacked against me to the point where I can barely even reach the boss screen, then I really know repeated attempts are going to be futile. If there are still campaign levels I haven’t finished yet, I’d much rather spend my lives on those, and if not, I might randomly go back and play a few campaign levels just for fun, but otherwise I’ll put the game down and go do something else entirely until I’m up for another free round of the Arena.
I’m ashamed to admit that I spent 60 gems on a DC boss not too long ago, and it was one of the really hard ones from Mt. Evernest that I mentioned having an intense hatred for, but I really thought I just needed one or two more birds to finish him off at that point. 3 new birds and I still couldn’t do it. That was a hard-learned lesson. Unless it’s a boss I know I can defeat and I just needed an extra bird or two due to a fluke that made it a little more challenging than normal, I’ll never do that again.