I think a voluntary annual fee would be best, or even selective. Obviously most of us have paid to be able to even post. If that is insufficient, it would be nice if we could get like a "ZHP Mafia Premium" where you pay a monthly or annual fee to not see ads. I'm running an ad block but if there's a revenue issue, this is a resource I find valuable and I'm happy to pay if it helps the place.

This is how WhatsApp ran in the day before Facebook. They had a monthly (or annual fee), but you didn't lose any features if you didn't pay. It would remind the user every 6 months or so asking if they will pay. For them, this strategy gave them enough money to keep the lights on and a little room to develop. Just a suggestion.