I also have the Doran unit and am happy with the performance. I, too, wish the batteries were replaceable, and will experiment with cutting them open and seeing what I can do with the batteries when they die. I, like some others, remove them if I am going to be stationary more than overnight. Not sure how long the batts last, but I am at about 2 1/2 seasons and they are fine. I rarely lose the signal with Doran with a 30'er and no repeater or additional antenna.
"If the women don't find you handsome, they should at least find you handy." - Red Green