1- I (not to see) him SINCE he (to be) 16.
2- I (to know) him FOR ages.
3- Things (to change) a lot SINCE our previous meeting.
4- It (to rain) SINCE four o'clock.
5- I'm sure he (to watch) us SINCE we (to come) in.
6- He (to be) here FOR over an hour when we (to arrive) .
7- I (to try) to fix this computer SINCE early this morning.
8- He (not to have) anything to eat FOR nearly a week.
9- It's three years SINCE he (to start) learning German.
10- He (to collect) stamps FOR the past twenty years.