Generally, loading half a dozen posts of average size is sufficient, though with smaller posts, you can load more. Putting a picture or two in the blog is not a bad idea at all, but a picture in each post will slow down its loading significantly. Be aware of the possible problems - and various solutions.
Loading the entire blog, on the main page, is not a good idea.
Auto pagination will limit main page size, if nothing else does.
If you try to load the entire blog, you will eventually run into the one known size limitation on Blogger blogs - auto pagination. You cannot bypass auto pagination.
You change the posts / page count from either of two places. The dashboard Settings - Posts and comments page ("Show at most"), or the "Configure Blog Posts" wizard ("Number of posts on main page"), both let you set - and reset this limit.
You can limit the size by days with posts, or by posts. It's your choice - but think of your readers. Many don't have extreme bandwidth - nor are the Blogger servers overly robust.
Settings - Posts and comments.
Configure Blog Posts.
A well designed blog uses Archives of various types.
There is no need to show all of your posts immediately - if your blog is well designed and written, then the last few posts should give the casual reader an idea of what the blog contains. Blogger offers us several accessories and techniques, that provide good alternatives to publishing the entire blog on the main page.
You can, without too much imagination, provide access to the rest of the blog. A main page view limited to "n" number of posts will be linked, by "Newer Posts" / "Older Posts" links, to additional displays of "n" posts, in an infinite chain of displays. The whole blog becomes essentially one main page, broken by main page size, into chunks of "n" posts each.
Note if you set "Show" to "7 posts", you'll get a total of 7 posts. If you set "Show" to "7 days", you could get anywhere from 7, to any number, of posts, displayed in main page mode on your blog.
As you become more skilled in developing your blog, whether it's a Classic blog, or uses the improved Layouts format with all of the new amenities, remember to keep it simple. Eventually, we will see design limitations, besides the limitation in main page view size.
The above the fold section of the blog should contain more content than ads.
Loading the top of the blog with ads is not a good idea either. When the reader opens the blog, he should see content.
Don't let the ads overwhelm the content - the top of the blog should contain no more than 1/3 ads, and 2/3 content. If the reader sees as much screen space taken by ads as by content, the perception will be that the blog is there purely to serve ads.
Most readers will go elsewhere, when assaulted rudely with ads.
Optimal page length is a subjective preference.
When is a web page too long? That's subjective, really. But look at how long (high) a page is. Take this page, for instance. You can measure its height, in one of 2 ways, depending upon the page height, the size of your display, and the amount of your patience.
- If your screen is large enough, stretch the height of the browser window, exactly until the scroll bar disappears. Now, measure the height. That's the simplest way.
- Look at the tab in the scrollbar, that you can "grab" with the mouse, and pull up or down, to make the page scroll. How high is the tab, in relation to the height of the browser window? If the tab is 1/2 the height of the browser window, you'll find that the page being viewed is 2 x the height of the window.
Look at the height of this display, as an example.
Here's an example. Looking at this post, Limit The Size Of Your Main Page, before I add this discussion.
When displaying this post, I see that the scroll tab is 1.125" high. The screen is 7" high. Scroll all the way to the top of the page. Now hit the "Page Down" button. How many times do you page down, before hitting the bottom? I count 5 times, on my screen. That means that the page is 6 x 7", or 42" high.
I don't have a lot of patience for counting, though. If the scroll tab is less than 1/10 the screen height, I'll have to count over 10 to page from the top to the bottom. So I prefer to measure the scroll tab height, and calculate page height.
Screen height squared, divided by scroll tab height, will also give you the height of the page. In my case, 7 x 7 / 1.125 = 43.5". OK, I eyeballed the measurements very roughly.
Either way, we're looking at between 3 and 4 feet of height. For my little post here, and that is from before I published this addition in it.
Look at scroll bar shape, and size.
Now, I'll use the width of the scrollbar as a reference. It's .125" wide on my screen. If the scrollbar tab is also .125" high (or square), on a 7" window, that makes the web page 392", or over 30 feet high.
I regularly encounter web pages where the scroll tab is square, or even rectangular (less than .125" high). Even 30 feet of text is going to take more than a few seconds to load. Many web pages of this height (and I have encountered more than a couple) contain high bandwidth graphics, besides being 40 - 50 feet high.
I would guess that somewhere between 2 feet, and 30 feet, is too high. Bigger - 40 - 50 feet, is absolutely way too high. Very precise numbers there, Chuck.
Maybe the best I can say here is, the next time you're loading a web page that is taking too long, calculate the page height. See how high is too high, for you. Or the next time that you (or your readers) have trouble loading your blog, look at the main page size, and cut it in half.
Note the setting only controls main page size.
Note that this setting applies only to the main page size. There is no similar setting, to control the sizes of archive or label retrievals - those are limited to 20 posts / page, as a fixed setting.
In 2010, Blogger introduced Auto Pagination, which will limit page sizes, and should make blog resource use more uniform. This will make Blogger more reliable, for everybody.
If you want to avoid the effects of auto pagination, consider using Jump Break. Jump Break is the most effective auto summarisation solution, for Blogger blogs.