I don't know about any settings regarding hovering, but in the design tree you can right-click the name of the plane (where you're hovering) and in the context menu that pops up, click show/hide to toggle the visibility of the plane (it's the pair of glasses at the top.)
There's "Dynamic highlight" in "FeatureManager Options" of system options,
But I don't see a time/delay setting. Don't remember hearing/seeing one either.
Is it for some docs or all? There's doc properties settings for planes too, but not really related to the tree.
Unless plane transparency has something to do with your issue?
Is this a recent anomaly? Is your graphics card/driver behind this? (guessing, obviously)
Are the affected planes hidden?
Yes, the dynamic highlight resolves that. I'm not sure how it got turned off. What I meant by the tenths of a second is when it's turned off, the planes etc. still show up for tenths of a second, but when it's checked they remain on for the entire operation. I stumbled unto this last Friday, but when I tryied it at home, it odded enough seemed to highlight the planes even when the dynamic highlight wasn't checked. I'm going to double check that on my home system, but for here at work, it's seems to directly control, whether they blink on or remain on.