And if the tree should grow half an inch?
Oh right, you cut it down to size ...

Stop being silly. A bonsai is a living and evolving work of art. It may be kept
approximately the same size for years. The grower may choose a different front,
may let it grow larger, or may cut it back & make it smaller, then repot it in
a different pot, just as a curator may sometimes put a painting in a different
frame.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)