The company didn't say whether or not there was an expiry date for the free Supercharging offer, although Electrek obtained a memo that didn't treat it as a limited-time promotion.
It's a notable change of heart, though not completely unexpected. When Tesla ended the incentive, Elon Musk claimed that it was "not really sustainable" with large-scale production. However, it's also clear that Model S and Model X sales are soft in comparison to the Model 3. This could boost sales by making it less expensive to own one of these premium cars in Supercharger-laden regions. On top of this, Tesla recently raised the base prices for both vehicles. While they're also more expensive to make, their higher costs could make it easier to offer free Supercharging without a hit to its bottom line.