Validation for my approach to putting down books I don’t like

My strategy for reading is pretty simple:
Finding books to read:
* Browse a bookstore or library, open books that picque my interest and read the first line. If the first line doesn’t convey the writer’s style and provide enough “oomph” to intrigue me, I usually won’t bother
* Suggestions from respected sources (friends whose taste I agree with, NYTimes [occasionally], blogs I read regularly)
What if I’m caught in a book I can’t enjoy?
* The first line was good, but 50 pages in, I’m still struggling to turn the pages? If I think the book might possibly get better, I usually push through another 50 pages and re-evaluate.
* If, at 100 pages in, it still sucks, I give up.
* All these books land in my “Stranded” category.

Now my approach is validated by the esteemed folks at Levenger: Tools for Serious Readers. Quotes from the article include:
“Many professional readers apply the 50-page rule. If the book hasn’t grabbed them by then, they give it the heave-ho.”
“Consider wine tastings. Do we finish the whole bottle for each wine we sample? Tastings wouldn’t get very far if we did.”