You can do your research and get your information anywhere, but make sure it's up-to-date otherwise no one is going to read what you're writing. The last thing you want is to give out wrong or inaccurate/outdated information. Also, make sure you're getting your information from other reliable sources. You can also take information from real life experiences, which was what I personally used a lot of when I was actively posting for my family/relationships, Familial Ramblings, blog (along with what I had learned at school).
In regards to how much time I take to write a post, to put it simply, it depends. It depends on how long the article is, what it's about and how many times I need to double check my sources. Familial Ramblings I was publishing 3 times a week because it was a lot of work and I was writing long posts. Each post took me at least an hour to write and edit (that was on a good day). For my photo blog, Fel's Photos, I post almost daily (I take Sundays off) and it doesn't take me long to post at all. That's because I don't write a lot, it focuses on the photos rather than writing a long informational post.
Either way, hope that helps, that's just my experiences though, which I'm sure are different from others.