My history was similar - after perhaps 7 years the Cipro stopped working adequately. Metronidazole alone had never worked for me, but I’ve been doing great on the combination of the two for about 5 years or so. I experimented to find the lowest effective dose, to keep the risk of side effects as low as possible. I also discovered that they work as well for me taken once a day, which makes it easier to separate them from psyllium, VSL, and dairy products.
Have you tried other antibiotics, like rifaximin (Xifaxan)? If you have two or more satisfactory regimens you can switch (rotate) between them every few weeks, and possibly lengthen their effective life.
If the antibiotics stop working or become unacceptable for other reasons there are a number of biologics you’ll be able to turn to, and they work in several different ways, so a failure of one doesn’t mean much.