People tend to avoid stuff that isn't going t bring them long term enjoyment.
Yes, most friends will not be with you trough thick and thin, but they will be there "now". You live "now". Not tomorrow, not the next week, year or in the past.
It is nice if you can get a friend for your whole life, but it's also nice to have one now. I remember all my friends and all the great time we had. Maybe we don't see each other anymore, maybe we moved on, found other friends, but the time we spent together was real.
So instead of thinking how the good times will end, think how it IS the good times. And when they end, you will be able to look back and say "I had fun".
But what if you don't search for friends? You will still be alone like when the friendship ends, but you won't be able to turn around and remember the good old times.
You don't lose anything, you only gain. So why not find some friends, even if it's just for a day?