Once you have a terminal spike the plant will never grow new leaves from the growing point, that's why its called terminal. But I'm sure you already know this.
It doesn't matter the age of the plant or the number of leaves the plant has.
Your plant may however produce basal keikis. As far as producing a keiki from the terminal spike I don't have experience with that but have been told its not a good idea to try for one there, something to do with issues with the tissue of the terminal spike.
I was also told that the best keiki from such a plant would be the one farthest away from the spike, the lowest on the main stem. Again something to do with the tissue of the plant. It would also be possible that such a plant produced from any keiki of a terminal spike plant may also end up having terminal spikes itself.
Sorry I can't be more clear but it's been awhile since I was given this info. The source of my info was from a phal grower of many years and much experience.
I would say that if you feel so inclined, go for it but just don't expect too much. You never know though you may get lucky. Always worth a shot in my opinion
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