Awakened Mind:

You can form a telepathic connection between your mind and the mind of another. As a Bonus Action, choose one creature you can see within 30 feet of yourself. You and the chosen creature can communicate telepathically with each other while the two of you are within a number of miles of each other equal to your Charisma modifier (minimum of 1 mile). To understand each other, you each must mentally use a language the other knows.

The telepathic connection lasts for a number of minutes equal to your Warlock level. It ends early if you use this feature to connect with a different creature.

For Awakened Mind, you have to be within 30 feet to initiate, but the link can last while you are miles apart.  However, the duration is only 1 minute per Warlock level.  The only use case for the "miles apart" after being "within 30 feet" after a few minutes would be if one of you can teleport.  Am I missing something or is that the intended reasoning?  I suppose I could jump off a cliff that's a mile down (less than a 40 second trip for the average human) and Feather Fall at the end and still have the link for a few minutes.

At level 20 you can potentially walk 2 2/3 miles apart before the spell ends. Add in horses or speed-boosting magic items, and that limit becomes very relevant.