Dental problems in 20 year old cat.

My cat Jack, who is 20 yrs old and has a predominant heart murmur and obviously a poor candidate for any surgery, has been diagnosed with a tooth abscess. It has been over a month since they have given him one injectable two week cycle antibiotic. He has reacted to the antibiotic and pain meds extremely well. His entire being seems to have changed back to a state that I have not seen in years. This is a good thing. At this time he shows no signs of pain or swelling and has not required any pain meds for several consecutive weeks. Is it possible to keep the infection at bay indefinitely with antibiotics on a regular basis? If so, should he be given a schedule for the injection, or wait until symptoms begin to resurface? We do not have the money to take the chance of his survival during surgery. We do not want to put him down unless he is in a constant state of pain and unable to continue a life of quality suitable for him.

Your advice would be most helpful and appreciated.

Sincerely,
Anne and Lance Schmidt