My amaryllis bulb has been blooming spectacularly for 5 years (2 flower stems, 8-10 flowers). I remove bulb from pot during fall and store in a cool, dark place for 3 months, then remove dead leaves and repot bulb. This year my bulb has 5 very healthy looking leaves, but no flower stem at all (for the first time). Does this mean my bulb is "finished" and unlikely to bloom again? Or is there something I can do?
Yes, bulbs certainly can become old and quite producing. Don't give up yet though, there are reports of Amaryllis bulbs lasting 100 years in warm climates, planting outdoors.
The lifespan not as long in forced and stored bulbs, but still reports of 30 year old bulbs.
It could just be an off year. Make sure you allow the bulbs leaves to die down naturally.
Here are some more links with information that may be helpful.