I have seen people say
'I am your age' instead of saying 'I am of your age'. Similarly, a sentence like 'you have done this your whole life' instead of 'you have done this for your whole life'. My question is: why for/of is omitted? Any gramatical reason?
Thanks in anticipation
Words are often omitted from constructions in English, usually where their omission does not lead to ambiguities or other problems. Prepositions sometimes may be omitted and sometimes must not be used (where one might reasonably expect them):
He stayed home. [more often US usage] / He stayed at home.
He went home. / *He went to home. [BUT He went to John's home.]
He looked out the window. [more often US usage] / He looked out of the window. [more often UK usage]
Would you just wait a few minutes. / Would you just wait for a few minutes.
A boy your age should be out playing football on a day like this. / A boy of your age should be out playing football on a day like this.
*She is leaving the morning. / She is leaving in the morning.
She is leaving tomorrow morning. / *She is leaving in/on/at tomorrow morning.
You have done this your whole life / ?You have done this for your whole life.
*You have done this many years. / You have done this for/over many years.
One has to learn individual usages.
It is a general tendency of English to drop prepositions when the meaning remains clear. There is no general rule and it would be difficult to draw a line where you may drop a preposition or not. Such shortenings seem to begin as an individual manner of speech and sometimes they spread like the circular waves when you throw a stone into a lake. When you study this phenomenon you will find hundreds of examples. One author may use in the same novel at the beginning of a sentence: on the next day/the next day/next day. The "to" in "help to do" shows a tendency to drop. Etc etc.
