What’s the optimal number of posts to have on your blog’s home page?

There are about 10 kazillion dependencies. Things you have to consider in that context are: 
1. HOW LOAD INTENSIVE IS THE BLOG; meaning how many images are involved in every post and how long is it going to take a modem user (yes, we still have them out there so don’t forget) to load the site completely if there are more then 10 posts on the homepage
2. WHAT FREQUECY does the blog receive new posts in? Which is necssary to determine because some people wanting to share a specific post (and are inexperience blog users) will not send the dedicated link to that specific post but to the blog its self. Now, if you publish 10 articles daily, the friend who received the recommendation email and reads it a day later because he’s a bit lazy on email too, will not find that article but the 10 new ones that have been published since the email was sent to him. 
And those are just two of them. But the most important ones. 
You’ll have probably set up a few blogs in your life. And software packages like WordPress draw from a long time of experience. So if their standard settings is 10, I’d say it all boils down to that, I suppose. 
If you need more help please feel free to contact me.