Celebrim
Legend
Flying is indeed a big shift in the game.
My general approach is to use house rules to put it off. If you make flight rare enough, it can be something a PC can do to solve problems, but isn't something that is pervasive. By the time it becomes pervasive, you should have already spent a lot of time with the characters doing more gritty things, and you can move on to a different 'tier' of play. For me, the next tier of play involves the PCs becoming connected to the world and ceasing to be purely self-interested. So, at that point, it doesn't matter so much that the giant purple worm can't fly and can easily be killed from the air. What matters is that if the PC's don't intervene directly and draw its attention, it will eat that house and in some sense the PC's will have lost even if they win. Also, if the characters are 12th level, you've probably milked dealing with chasms and pit traps for about all its worth (for now).
But yes, this is a huge adventure design consideration. The thing is, I expect it to happen. I know, "Once the players are above a certain level, the problems of long distance travel aren't a huge obstacle to them. If I want to do a wilderness exploration campaign, I have to do it before the players hit 10th level or so."
My second approach is to make flying less safe and convenient than the rules provide for. For example, if you are hit by a dispel magic in my game while flying, you will not gently float to the ground. And the third level of version of flight in my game, "Hawk's Flight", literally gives the character wings. Only at 4th level can you get wingless flight, and then only for 1 round/level. Winged flight is highly inconvenient compared to the sort of flight provided by the Fly spell. Flying isn't usually really problematic until it involves non-facing, the ability to hover, the ability to ascend and descend vertically, adventuring day long durations, and so forth. Flying steeds are inconvenient and can be killed. Brooms of flying are problematic to ride comfortably or safely for long distances or in adverse circumstances. Flying carpets are potentially amazing, but are fragile and still limited in maneuverability. You don't want to be on your flying carpet when hit by red dragon breath, because on a failed save I will also make the carpet save or take damage, and then you're going to be adding injury to injury by losing your expensive magic item and falling out of the sky.
My general approach is to use house rules to put it off. If you make flight rare enough, it can be something a PC can do to solve problems, but isn't something that is pervasive. By the time it becomes pervasive, you should have already spent a lot of time with the characters doing more gritty things, and you can move on to a different 'tier' of play. For me, the next tier of play involves the PCs becoming connected to the world and ceasing to be purely self-interested. So, at that point, it doesn't matter so much that the giant purple worm can't fly and can easily be killed from the air. What matters is that if the PC's don't intervene directly and draw its attention, it will eat that house and in some sense the PC's will have lost even if they win. Also, if the characters are 12th level, you've probably milked dealing with chasms and pit traps for about all its worth (for now).
But yes, this is a huge adventure design consideration. The thing is, I expect it to happen. I know, "Once the players are above a certain level, the problems of long distance travel aren't a huge obstacle to them. If I want to do a wilderness exploration campaign, I have to do it before the players hit 10th level or so."
My second approach is to make flying less safe and convenient than the rules provide for. For example, if you are hit by a dispel magic in my game while flying, you will not gently float to the ground. And the third level of version of flight in my game, "Hawk's Flight", literally gives the character wings. Only at 4th level can you get wingless flight, and then only for 1 round/level. Winged flight is highly inconvenient compared to the sort of flight provided by the Fly spell. Flying isn't usually really problematic until it involves non-facing, the ability to hover, the ability to ascend and descend vertically, adventuring day long durations, and so forth. Flying steeds are inconvenient and can be killed. Brooms of flying are problematic to ride comfortably or safely for long distances or in adverse circumstances. Flying carpets are potentially amazing, but are fragile and still limited in maneuverability. You don't want to be on your flying carpet when hit by red dragon breath, because on a failed save I will also make the carpet save or take damage, and then you're going to be adding injury to injury by losing your expensive magic item and falling out of the sky.