With the pro subscription it usually takes less than thirty seconds for the songs to be playable. It keeps generating while you play though, so the whole audio file isn’t available for a few minutes.

Free accounts are queued so it depends on load and I don't think the v3 model is available to them.

The v3 model is now available to free accounts. Normally takes me a minute or so at most on a free account to generate a song. Though, as you said, it does seem to depend on load.