One of the big SEO questions we're often asked is: how long should my posts be? Specifically, do longer posts cause problems with pageload speed?
Since search engine algorithms are always changing, the answer to this question will vary too. However, Google has been penalising thin content recently, so very short posts are not recommended.
On the other end of the scale -- how long is too long? A good rule of thumb is to make the post as long as it needs to be to say what you need to say. Don't pad it out with waffle just to make it longer! It's important to remember that some users don't have fast Internet connections and/or pay a lot for data so you want to make sure that everything in the post is giving the user bang for their buck.
When considering pageload speed on long articles, it's worth knowing that wordcount isn't a big factor in performance: it doesn't take many resources to load text. However, the content needs to be engaging because users drop off the further down the page they have to read.
Photos are a different story -- depending on the size of the photo, they can use a lot of resources. All photos uploaded to sites on Performance Foundry's hosting packages are optimized on upload, which helps. However, it might be worth including fewer photos in long posts: use them strategically and maybe a little more sparingly than you normally would.
Depending on the subject matter, it might be more advantageous to create a content hub with several separate related articles interlinked with a master one, instead of one enormous article.