I was thinking about this as I took out the air filter the other night. The filter is pretty darn sturdy.
I don't see why you can't just vac it and resuse it. Sure it wont' get cleaned 100% from a vac, but all the loose dirt will come off.

Only issue I can think of is that eventually the paper media weakens from TIME and the lodged dirt that couldn't get vac'd is sucked in.

 

people been blowin out filters since the beginning of time

 

Buy a new one, it's cheap.

 

You could probably extend the amount of time the filter would be effective by vacuuming it like you've described. Maybe a few thousand miles worth. But much of the microscopic dust that's firmly embedded in the media would probably remain. I'd probably just get a new one since they're not too expensive.

 

I don't have a problem with this as long as its still replaced as you would normally. Like said above you get a lot of small particles stuck in there, just because you got all the leaves and big stuff out doesn't mean it's all good. I'd still replace it every 20-30k depending on regional area.
And with blowing it with air, just don't hold an air nozzle with 150 psi directly on the paper. If it starts to separate in an area that you can't see and you re use it, your motor will ingest it. Just be sensible with it.