Any reader worth using should have a settings or preferences section where poll interval can be configured, which should address the main issue in the article. Other problems like incorrect If-Modified-Since headers are probably not easily discernable without looking at source code or pointing the reader to your own page and checking the logs.
I am using inoreader (cloudbased), which seems to adjust its polling rate depending on how frequently the feed was updated in the past and how many users are following it. This seems to be between 10 minutes for things like the verge and 60+ minutes for smaller feeds, but I am not sure, if it also takes into account rss header information.
The Feed of the blog of this post seems to be refreshed every 6+ hours, but idk why that is.
