1.

2.

Time expressions with for show the length
of the situation or action--or how long the
action or situation continued. These time
expressions show periods of time. Use for
with periods of time, not with specific times:

not this: I have lived in Phoenix *since
nine years.

but this: I have lived in Phoenix for nine years.

not this: They have been here *since two days.

but this: They have been here for two days.

3.

Periods of time can be shown with or
without for:

I've lived in Phoenix for nine years. /
I've lived in Phoenix nine years.

They've been here for two days. /
They've been here two days.

He's had his car for exactly one week. /
He's had his car exactly one week.

4.

Some verbs are "one time" verbs: they
cannot usually be used to show an action
or situation that continued:

not this: I have *moved to Phoenix
for 10 years.

but this: I have lived in Phoenix for 10 years.

not this: He has bought his new car
since last Tuesday.

but this: He has had (or owned) his new car
since last Tuesday.

In the examples above, move and buy are
"one time" verbs: the action or situation that
they describe did not continue. In the situations
above, the "one time" verbs should be past
tense, not present perfect tense. Also, in order
to show the action that continued, a different
verb is needed.