Can't remember exactly how long, but probably until DD was about 2yo, possibly longer.
I found it fabulous to be able to change at 'my height' rather than getting down onto the floor. I had a fold up change table I borrowed from my sister, but this time I bought a change table with drawers under it that the top flips over to become a shelf above the drawers so we can keep them in the room 'forever'.
Cheers,
Rachel