Honestly I don't really believe in the concept of "friends for life" at all. I actually think it's a bit of a damaging concept really. Yes, sometimes you might become friends with someone and circumstances mean you remain in contact for the rest of your lives. However for most people, you make friends relative to the exact circumstances you are in, and inevitably when they change for one or both parts the friendship usually fades. That's not a moral failure or anything on anyone's part, it's just the nature of life.
It's far better to focus on your friends for the situation you are in, and appreciate them and engage with them actively while you are in that situation, than trying to weigh up whether they are "friends for life" and miss out on the experiences now. Make new friends and focus on enjoying it while you are there in the moment, and if it doesn't work out longer term recognise you can and will make new friends later too.