Most of the visitors tend to be those who do not expect more than a minute to load the main page, either a blog or a full fledged website.
That is why visitors despair at some point when entering a blog, the scroll bar of the browser window starts to become smaller until it almost disappears.
Visitors try to go down the blog to see the different entries, but do not usually get beyond the fourth because they know they have way too long to go and also begin to feel dizzy.
Limit entries on the main page is an option on most publishing systems: WordPress, Blogger or any others. So, virtually nobody has an excuse.
In Blogger is easy, just enter the Control Panel, Options -> Format and select the number of entries to be shown on the homepage. Forget the choice of days, because, as warned, set the limit, if one can call limit to 999 entries.
In WordPress, it is the same, simply go to Reading option and set the limit of posts to be shown on home page.
If your blog is full of images, to load more than 10 entries can be very heavy, considering also that not everyone has a broadband connection.
There is no ideal number that how many posts should be shown on the homepage; but try to keep it below 10. For us, 5-7 works great. You also have to match with the length on the sidebar content. Posts should end where the last sidebar widget ends. This setting makes the page looking more compact.
On the other hand many will end up dizzy and leave your blog, no matter how good your content, but will not read it.
If you do not believe it put all your posts on the front page, that is not going to get you to read, and will happen just the opposite. A well structured blog, that offers a navigation facilitates for searching posts, help people to dive into your blog, that works better.