[elcritch]

When I read most papers, it will be to do what you say. There are many papers which really aren't worth spending more than 20 minutes perusing since they just rehash or tweak something which was done previously. Unfortunately with the publish-or-perish mentality predominant in most of academia, I'd say this is getting far worse and likely to increase. Sometimes I wish there were a "goodreads" or "netflix" for scientists.

Now, a good paper I will read and grok the main importance in a few hours to the point I can implement the basics. But, a classic paper will be like a well-thumbed classic and might take years to fully grasp.