It all depends on where you are cycling. Usually Early to mid-June, the season hasn’t fully kicked in yet, so hotel rooms should be available without too much notice. In July it might be hard to find accomodation without a few days notice. Especially in top tourist destination areas. In places like Lofoten usually you will need to book many weeks in advance. In addition, it’s also based on how much you’re willing to pay. Usually, high-end rooms are available last minute, but budget rooms will be booked up days, perhaps weeks, in advance (Lofoeten months in advance).