Hi Oregon,
Your speed and acceleration, especially from a standstill, will also reduce range from that 'ideal' 40 miles, though your light weight is very much in your favour. Maintaining momentum when possible to avoid stop/start situations and accelerating gradually & smoothly where possible will noticeably boost your maximum range, as will using smooth rolling tyres at good pressures.
I think if you have any moderate gradients or have to stop/start much, if you get much over 30 miles you're doing well.
I hope you enjoy your new bike & do let us know how you get on when you've tried it out, if you can pull yourself off it!
Stuart.