Musician’s mathematics

A fictional calculation:
If you want to survive let us say you need 42 gigs/concert a year (not meaning feeding a family of four ) with average standard payment of small concert series and poor guitar festivals and not having the support of a major record company.
It is always something special if a presenter hires you every year, but sooner or later it turns into a rhythm between 2 and 5 years to return, so let us count with 3!
If you write 100 concert proposals you will get around 70 times no answer, 3 YES, and the rest something between clear “no” and “let us stay in touch, maybe next year”
In my beginner’s years it was 90% with no answer!

So numbers:
42 gigs a year meaning 1400 letters (980 no answer)
In three years:
126 gigs meaning 4200 letters (2940 no answer)

Correct if my I calculated wrong… but for sure it means that you need a BIIIIIG addressbook!!
How many letter do you write each year?