Hi irish_seeker

Did you include a Self Addressed Stamped Envelope with your letter of Request?

Usually, it doubles your chance of success

Fanmail

Well being that these some people you sent to are "very famous" , no. Don't be worried.
They are just busy and have a lot to do. RELAX, get a secondary hobby and wait until they arrive.

They WILL come.

Just outta curiosity who did you send to?

It may depend on the individual and what their reputation for signing is. You may want to try and research each person to determine as to whether or not they have a good reputation. Also, did you include a SASE & item to be signed with each request? If not, that could factor into it as well. Collecting autographs can be very hit or miss. Sometimes you get lucky and sometimes you don't. You just have to keep trying. Good luck!

So I sent about 20 letters about 5 months ago to some very famous and some not so well known people, and I haven't revived any of them back. Should I try again or wait a few more months?