On my account, I have a few items where I set my real address to the exclusive sender (as in, I'm letting everyone use this address without changing the counter) -- it's great for a RSVP link (then after the party, I set the counter to 5 just to catch stragglers and anyone after that I don't really care).
But I tried to set up an account for my friend for a blockparty he's organizing, and that doesn't seem to work anymore (the counter still went down).
Is there a "right" way to make an address wide open for a time?