It sounds as though your amaryllis bulbs aren't storing up quite enough food to rebloom. I also think you are giving them a little too much time in the basement. Here are some tips that should help your plants rebloom. First make sure the plants get enough sunlight on your porch to recharge-at least 6 hours of direct sun a day. The plants require fertilizing when they are up and growing. Use a liquid houseplant fertilizer once or twice a month at half the recommended strength. By the end of the summer, each bulb should produce 7 to 11 leaves. Keep plants moderately moist until their leaves begin to yellow in late summer, then give them a good drink. Wait until the soil at the top of the pot is dusty and dry to water again.
At the end of the summer, cut back on the water even more until the leaves die back. At that point, stop watering completely. Bring your bulbs back inside before the first frost, and store them in a cool (but not too cold-this is a tropical bulb), dark spot. After about 2 months, pull the bulbs from the soil; remove the dead, dried leaves and roots; and discard the soil. Repot the bulbs in fresh potting soil and water thoroughly. You should see new growth fairly quickly.
Once top growth begins, move the pots to a sunny window. Flowers should appear about 6 weeks after replanting. As the flowers fade, cut them off behind the swelling at the base of each bloom so the plant does not waste energy forming seeds. Let the stems and leaves die down naturally. As long as they’re green, they’ll be putting energy into the bulbs for next year. Once all danger of frost is past and nights are consistently above 50 F, you can move the pots outside and start the process all over again.