I have a similar B&D electric. I find that I need 25% to 33% overlap
to do a good job. 50% if the grass is rather wet. Also, mowing a
little "long" seems to behave better -- less "tearing," so to speak.
As to sharpening, I do it once a season. Just use a file, clamp the
blade in your bench vise, and "draw file" ALONG the blade, maintaining
the contour of the bevel. A fairly course "mill *******" file works
well. A little grease on the threads on the shaft help to keep it from
getting corroded. Here in "Slower Lower" Delaware, it is quite flat. I
have about 8,000 square feet, and can cut it in 1 1/2 hours, not
pushing things too hard. Another 1/2 hour for trim, etc. I am quite
pleased with the B&D electric mower. Got it refurbished for $99. Can't
beat that. BTW, also lube the bearing for the wheels now and then.
Heavy oil (SAE 80 gear oil) works well for me.