Well, my good friend,Mr. Mihir Mulay in his blog "A literal confusion"...http://pencil-thoughts.blogspot.com denies the fact that there can be more than one "best friends".So this insists me to write my first blog in opposition to that, based on my personal experience.........
To start with ,I want to ask "how do you define "best friends"? He\she is such a person with whom your wavelength matches,is such a person you want to be wih,and open your heart to, who will guide you correctly, who will stand by you in times of need,who will encourage when you are low ,as also bring you down to earth when you are floating in the air of pride and last but not the least who knows you even better than yourself........
In a time span of 30 40 years if you see,[after you learn to understand and think rationally],you meet many people.Also the intensity of relationship increases or decreases.But still there is certain feeling that still remains.
To elaborate on this I would like to give an example. You have a best friend in school.After school eventhough you are not in touch with that person so much, the feelings are still the same.During that period you go on making new friends.... And amongst them you might find another good friend.. so good who can be your best friend also. So here "the superlative term" crosses its limitation or in other words its world expands...!
If you are lucky enough that you meet people matching your frequency, so now more and more good friends turning your best friends!!
No doubt, time span is a factor that decides the number of best friends that you make. But at the same time if you are rigid enough convincing yourself the fact that 'so n so is my best friend,' then you only close the door that will lead you to many good friends out of which some can be your best friends.Thus creating an exception for the so called "superlative term"in english language.
Maths theorems can have rules ,as also physics formulae.But the term "best" for the "many" friends can also surpass the grammar laws......!