He didn't say it after the referendum, it was before the referendum. The point of saying it was to emphasise to voters that the Tories had sanctioned this one off opportunity, and we might not get another chance for a long time.
He wasn't specifying any timescale before we can have another one, just emphasising how important the referendum was. And it wasn't an emotional poor choice of words, after the event. It was written into the "Scotlands Future" document. He was basically saying to voters, not to expect to get a second chance at this as there is no guarantee that Westminster will allow us to have another go. So far he has been proved correct.
"557. If Scotland votes No, will there be another referendum on independence at a later date?
The Edinburgh Agreement states that a referendum must be held by the end of 2014. There is no arrangement in place for another referendum on independence.
It is the view of the current Scottish Government that a referendum is a once-in-a-generation opportunity. This means that only a majority vote for Yes in 2014 would give certainty that Scotland will be independent."