If Bashir had never done that experiment which caused Data’s programming to activate his ability to dream, how long would of it taken him to dream? It was programming which was meant to activated at a certain point of his own personal growth, so how old would he of been for it to happen naturally?
You could ask, would of it happened at all, but Doctor Soong was clearly so sure of Data’s ability that it would happen. But imagine if the accident didn’t occur, and Data felt tired one day and closed his eyes, for what he only thought was going to be a moment, at the helm of the ship during some routine scouting of planets and he has a really intense dream and it lasts about an hour, and when he comes too Geordi is over him scanning, Deanna holding his hand, Picard is on the comm to Beverly trying to keep it together, Riker is not keeping it together, and Worf has ready torpedoes while growling lightly.
Then after an hour of Data explaining his dream, in full detail to the entire bridge crew (and Beverly on the comm) the scouting mission carries on, but Picard has yet to stop face palming.