Hi Anonymous! My advice is: don't worry about such things! These are PROFESSIONAL firms! Of course you might apply again in the future! I believe it's quite the opposite - if they know they had already extended you an offer in the past, then they know that you are a very interesting candidate for them and there is no reason to not trust the judgement of the colleagues who interviewed you in the past.
I can even give you a personal example: Bain interviewed me twice for full time positions (two different geographies and 3,5 years between the processes) - and I declined their offers twice. Was this a problem? No of course not. They acknowledged that my alternatives were apparently better at both occasions. That doesn't mean they would not interview me in the future (if the situation emerged).