And how big the conifer is now, how fast it grows under the conditions provided, how long the potting medium maintains its integrity... You'll just have to forge ahead and see how it turns out.
Hi, I have seen a Wollemi pine at least 2m (6.5feet) tall growing very happily in a pot - perhaps 50cm (20") diameter. Good luck Brian
Here is my 3 feet wollemi pine, new growth looks very strong this spring. This is the third year with me and I re-potted it as many times.