I have crimson king in a large pot. Am sure that it will be happy in it for 5 years or more. If you keep it pruned then I think you could keep it long term, if you allow the crown to develop then it will be top heavy and will fall over in strong wind.

Thanks Kildermorie - would you know what kind of compost if needs if I keep it in a pot?

I put in some gravel at the bottom of the pot for drainage, garden soil (clayish) and compost mixed up and then the tree. I bought mine bare root and it came on fine.