Most obviously, or maybe not, the best time to add posts would seem: before your readers tend to go to your blog.
This may mean you are adding blogs at 6:00am to catch the morning crowd.
However, there may be other considerations as well. For example, where is your readership from? Are they mostly from North America? If so, you might need to reconsider timing.
If you get lots of traffic, and a steady readership then you need to maintain consistency. People will keep coming back if you have something to say and if they know what to expect. However, if you are doing things in big bursts (for example, 5-20 blogs at a time) and then none for a while, people might forget about you and let you dwindle in the dust.
Another thing to consider is how to get your blog out there. If you haven’t already, add a “Follow this”, “Tweet this”, “Like” or some other social network button to allow people to share with others. You want people talking about your blog and hopefully even commenting on the posts.
Keep it up. Keep it steady. Make it interesting and relevant.