i leave mine alone, if they are green and alive. eventually most will produce more flowers. i don't do this competitively, so i like to have even a few flowers. i have had my plants grow new leaves and roots even though there was s till an old flower stem, and grow while flowering, so i'm not sure one way is better than the other. may be a matter of taste. i had a red phal that sent out side shoots for about 2 years from one old spike, and in the meantime it sent out another new spike and they both still produce a few flowers at a time. others drop their old spikes right away, so maybe breeding affects them? as long as they are not unsightly, i leave them alone.