Depends on the intended use. 72ppi (pixels per inch) is fine for screen viewing but will print blurry. And your average printer (<$200) can only print 600dpi (ppi equivalent). A 72ppi file is smaller, while a 600ppi at true 8.5"x11" size will be gigantic.

My suggestion: downsize it by half (4.25"x5.5") and scan at 300ppi then check the file size. Even a jpeg compressed by half will print okay.