Chocoholic, your assumption is incorrect: the red flag on a mailbox is for the postman or postwoman to know that you have a letter to be mailed in the mailbox. It is not for them to hoist up to let you know the mail has arrived.
My mailbox has a secondary yellow flag that will automatically go up once the mailbox has been opened & then closed, indicating that someone presumably put letters in there. If you want to know you have mail, this is a simple solution. Here's a link to Home Depot for my exact mailbox, but I;'m sure there are similar ones if this one isn't to your fancy. (Note: you can move the yellow flag to the other side of the mailbox if that gives you a better view of it from the top of your long driveway).
I have a long driveway myself, so I feel your pain when it comes to checking for mail!
https://www.homedepot.com/p/Gibraltar-Mailboxes-Patriot-Black-Large-Plastic-Post-Mount-Mailbox-GMB515B01/207205059