[graycat]

It is extreme; too many people do do it, but I was warning them that they shouldn't do it. Why? It's a super good way to get totally stuck-o and give up, all for no good reason at all. And if work on such a tough exercise full time for two weeks, as I did a few times as a ugrad or in some of my later independent study, then that's mostly a waste of time.

Although too many students do this, for the OP it was a straw man to have something to knock down so that they could say something else. Not good. The exercises are one of the best aids to a good student trying to learn; but, can do well working 1/3rd of them, or half, or the more difficult 1/3rd, or 90-99%, but on that last 1% can spend more time than on the first 99% and just shouldn't do that. Don't worry: In any decently well written book, if get 90% of the exercises, then have done well. If really insist on the last 1%, cover the rest of the book and then come back with the additional understanding and maybe some crucial results didn't have the first time through. If really want to know the material well, then get 2-3 competitive books and work through those also.