Do you actually see unacceptable delays on your layouts or is this a general question?
Slower CPU's (iOS devices) or data transmission speeds (Host is not on the local network ) can make layout updates much more of an issue. The basic rule is "less is more". When you get a layout that is not updating quickly enough, take steps to simplify your layout and reduce the number of objects displayed at one time. You can use Tab controls and their cousins: Popovers and Sliders to display fewer objects at one time. Or you can create two layouts where you have one with fewer objects on each with a navigation button to change layouts. Reducing the number of unstored calculations, filtered portals and conditional format expressions will also help.
But I wouldn't make major efforts in any of these directions unless I am getting actual delays. FileMaker 12 went through a number of bug fix updates and improving layout refresh speed was one of the purposes behind at least one of those fixes so recent versions on a fairly decent computer seem to work pretty well here on my systems.
Yes, I do see delays. I have already minimized the use of conditional formatting and aggregate fields on the layouts. When I do to a new record or change layout modes, I see each field and object reload on the screen. The article I read said that there was a way to make FM not reload these elements each time I move to new records or layouts. I believe the article was outside of the FM Form. I've tried searching for the article again but cannot find it. I'm hoping someone can help me with this or if someone is familiar with this article.