I'm with Howard on this one. I always cut the spikes when it's done blooming green or not. Ultimately you want a strong healthy plant. Old spikes suck a lot of energy from the plant that could be better spent growing new leaves and new roots. Giving it a chance to recover and store energy will give you much better blooms the next cycle. I've even had plants throw mulitple spikes the next season. That said there are those plants out there that just seem to have to be in bloom all the time. You can cut off their spikes and 3 weeks later it's growing a new one.
David if the spike is yellowing it's on it's way out. May as well cut it now and get it over with.
