The Suzuki manual specifies replacing the cover as soon as the fluid is topped off before starting the next round of bleeding. I do find that excessive. Cover off or on makes no difference as to the movement of air out of the line. The action required to allow an air bubble to escape on its own is to tie back the lever. That opens the passage of fluid between the line and the reservoir. Taking the cover off does not. Keeping the lever tied back overnight to let bubbles migrate is a good idea. Leaving the cover off overnight is a bad idea. That's what I was addressing.Most manuals call for opening the cover on the brake to bleed the brakes, apparently the company that makes these things doesn't know how to work on them?
I did install the same banjo bleeder from Blair at SV Racing ($19.95 if I recall correctly?). It installs below the front brake master at the top of the brake line. Brake bleeding is tedious and so any tricks such as Mity Vac are welcome and for me the banjo bleeder did "seem" to speed up the bleeding process. There are many important steps in doing a proper bleed as others have noted in detail. I am not a mechanic but I did follow the advice of many who seem to be in the know and I follow directions diligently while I am learning.