[dahinds]

A close reading of a scientific paper of any consequence does not take half an hour. These days a published paper may typically be only a few pages but it isn't at all uncommon for the paper to be accompanied by 20-50 pages of supplementary text. When I'm asked to review a paper it takes me the better part of a day, at least. If I were a senior author on that paper that would be the bare minimum that I'd consider an acceptable commitment of effort.

[tokinonagare]

It really depends on the field. @londons_explore is right that a lot of papers in some fields can be read in half an hour, or an hour, and sent back with feedback.