0:45 General browsing: HN is a relevant news source for some subjects that I care about. I am entertained and happen to learn some thing along the way. Although I am not on the HN website the entirety of this period, I am reading in-depth article through links which HN provided.
0:45 Targeted learning: As a new hacker, I find HN's current article and those from the archive invaluable resources for understanding the community's response to new frameworks, technologies, etc. I use HN as a supplemental textbook to learn about use cases and some nuggets of wisdom
0:30 Giving back: I hate to only consume content. I'd rather have a seed:leach ratio of at least 0.33. This is my half selfish, half altruistic way of bettering myself and hopefully helping others. That's also a way of forcing myself to internalize my experiences and provide some analysis.
Just to answer your question - a good 30 mins additional on HN platform works very well for me to check on things that we may have missed out.