How often should a person empty recycle bin on computer?

There is no concrete answer to how often one should empty their recycle bin.

There is no difference whether a file is on the recycle bin or not. When you delete a file and it is sent to the recycle bin it's actually not deleted at all, the operating system only stops displaying it on the original directory and display it on the recycle instead. When you empty the recycle bin, the files still exist on your hard drive and are still recoverable via file recovery software. However, now the operating system will allow those files to be overwritten by new files on your hard drive.

So if you often find yourself needing to empty the recycle bin my advice are the following:

if you are sure you will never need the file you are deleting ever again use SHIFT+DEL (Permanent deletion) to delete it so it doesn't go to the recycle bin in the first place.
Don't delete the file at all if you are not sure whether you will need the file in the future as there's no difference for your hard drive whether the file is on recycle bin or not.