images per .xhtml file

Greetings,

Recently dealing with some images I had doubts how many should be included per page.

What's more convenient, filling the ereader RAM to the max with images in order to reduce internal storage I/O, or fill every .xhtml file with a fewer images?

With these two configurations, what would be a smoother turn page experience?

I am not to familiar with epub image loading and its optimal epub formating.

I'd be glad if anybody can throw some light on this matter.

Thanks in advance.