Squidward says in "Squid's Visit" he never visited SpongeBob, but he has been visiting him occasionally throughout the series.
In "To SquarePants or Not to SquarePants", the store owner tells SpongeBob they're not expecting a new shipment of square pants for months. However, three days later (at the time of the episode's narration), SpongeBob is wearing his square pants again.