I have managed to put off the installation for now but know I will have to let the installation proceed very soon.
No you don't, you are under no obligation to install Windows 10. Microsoft are not forcing you to have it, the choice is yours. I admit that it is "opt out" rather than "opt in" but the choice is there.
You don't say what OS you have but Windows 7's End of Extended Support is not until 14 Jan 2020