I understand that reviewers are quite busy and have not only a single paper to review. But, no matter how busy someone is, it should not take more than 2 minutes to reject a review request.
How did I get this question to my mind?
Well, it is a common question for everyone in academia, I guess. I am quite frustrated with the peer-review system and yes, I am impatient. Because after doing a lot of hard work on something and then achieving something real good out of this, which would lead to potential dissemination, turns out to be depressing.
We had submitted a work back in December 2016. Since February 2017, It was Under review. Suddenly, I see that it is Reviewer assigned. This system is really pathetic. Other parts of my question can be inferred from this.
As a reviewer, I don't reject the requests for review after 4 months. I would do the same within at most a week.