It is for me, anyway. Maybe Sublime has tricks I'm missing?
It's common that I want to do multiple find/replaces operations on a block of content. My experience is that once I've selected the block and opened find/replace with alt+cmd+f (Mac), most any move I make disappears the selection background. This may be a function of the scheme/theme I'm using.
* Enabling or disabling regex seems to unselect my block.
* Doing a find/replace (with Replace All) unselects the block and closes find/replace.
I'd rather Sublime leave my selection in place and leave the find/replace tool open until I dismiss it.