If I see ANYTHING coming up behind me I move over even though I don't intend to stay long in the passing lane anyway. When I use it I intend to pass something and generally get right back over unless they are stacked up in the right lane then I'll run it longer however if nothing is in front of ME holding me back and someone faster comes up I get over.
I do that in anything I drive.
And it's not so much people pissing me off there are those that seem to be bred entirely for that single purpose in life, it's the safety issue. Me I'm not prone to jumping and thus swerving, that's not to say my wife who is a very new rider wouldn't.
If some ******* blew by us like that and she went down the only thing that would save his ass or their collective asses is I'd have to stop and see to her.
speaking as one rider in CA ... although we split lanes a lot, that doesn't mean that we just let guys blast thru in the same lane. it can happen ... but the proper way to do it is for the guy behind to hang back and wait for permission to pass. since you are (hopefully) using your mirrors a lot, you should see him approaching from the rear. he hangs back when he reaches you - and then you wave him through when you feel the time is right and the spacing will be OK.
I'd get pretty pi**ed off if guys started blasting thru at high speeds in the same lane ... it's a dangerous way to live. after all, if he hits your bike then there's a good chance you both go down. and if there's a stupid cage following close behind, that means one (or both) bikes go under the auto that is following. NOT good.