If by "view" you mean workspace (aka client-spec), then I strive to have one client spec for each branch I am working on. I'm assuming by branch you mean you have a typical system where you have mainline, development branches, and maybe release branches too?
The reason for keeping the 1-1 correspondence is it just keeps things simpler. It can also prevent accidents - e.g. when I am in a development client spec, I know I cannot accidentally look at or modify a file of the same name in another branch. This can be a big help when you are down in the depths of a deep source folder hierarchy.
Keeping views "tight" is generally good practice in Peforce - as in anything. It helps server performance, which in turn helps performance of Perforce on your client machine. But beyond performance, I think the concept of only seeing what you need to see - letting the computer do the filtering for you - is just generally a good thing. It lets you concentrate on the job at hand without distraction.
I don't have any difficultly switching workspaces, and there are a number of ways to do this depending on your circumstances and preferences. P4V has a simple drop-down at the top of the left pane, for example. What difficulties are you having switching workspaces?