Hi Ian,
Yes you do need to reinvigorate the website from time to time, I am not sure if a forum based website like this one would be big enough for you to earn a full time living from it but as you say you need to give it a try... I would like to say to you, why not a user pays membership subscription fee to help with your costs, $5.00 a year or to get you a kick start ask the members for a $50 one off fee and $5.00 per year after that, some won't like it and you may loose them but if as you say you have 10,000 registered members even if 50% give you the one off $50 that's $250,000, that should help you to upgrade and cover your costs for a while.
Like I said, you will probably loose some members but I think your site is very well established and with a loyal following and I am sure if you explained to everyone what the money will do for them, as the end user, the fair minded people will fork it out and let's face it there is nowhere else to go for Rec Flying info etc here in Australia.
Just my thoughts Ian...good luck with it mate.
David L