Good news on the visit from the AC guy, Granny - hopefully it really was just a dirty filter. I know it can be hard on a budget, but it's best to change them every 30 days. What you spend on filters will pay off in savings on the power bill, etc as a clean filter makes the system work a lot less hard to maintain the temp you want and the harder it works the more you pay on that power bill. Admittedly, I don't get it done that often (which is sad given what I do, er did, for a living) but I do try to remember at least ever two months. The more "stuff" that is likely to be in the air of your home to get filtered through there, the more often you need to do it - pets, etc contribute a lot of hair, dust, etc. Some of the electric companies do energy audits and whatnot for free on homes and give you packages of "goodies" (lightbulbs, filters, etc) that can be used to improve energy efficiency - something to ask about next time you have them on the phone.