He would only stop eating after a big meal
All the eels I ever owned fed well every other day, not every day or two. You need to think of it, eels in the wild not feed on the daily bases or so, and often not feed for weeks at a time. Eels, in a home aquarium I have to say isn't all that healthy for the hobbyist will feed all too often and this im afraid will gain much body fat and cause liver malfunctions or better to say, a liver disease.
You should had been feeding that eel every 3rd day at most, and fed the eel until it refuses further offerings. One of the problems in this is when keeping eels with other fish, you as the hobbyist must learn on just how much your eel can feed on and make its diet as nutritional and as variety as you possibly can.
Also read that they could go a long time without eating and would eat less as they got older
That idea is kind of a hit and miss way of thinking. The truth to it it that when your eel such as a dragon moray when fed well, can go the week without feeding. The thing there is, in the body size of an adult moray can hold much more food then when it was a young juvenile. I had a large number of eels that not fed for 5 or 6 months and it never giving me any concerns.
One of the tricks of that when any eel gone on a long hunger strike, I began to offer smaller strips of fish or so. Like the male dragon that I sold, he was feeding on 9-10 inches long of fresh fish wight was less then 2". And when I make the strips smaller due to their long hunger strikes, the width was a inch or slightly less.
I offered you all my experiences with the eel, you can take it for what it be worth. But in all, the few things in which I mentioned at the start, all work hand in hand to maintain and keep your eel healthy for many years. The pair of dragon eels that I sold more then 18 moths ago, I had the female the longest, for more then 14 years.
Buddy