Digital BW, The Print

I've just bought an HP 7660 to use with the 59 cartridge printing B&W on the 
HP premium plus photo paper matt, and am concerned by what appears to be 
high ink usage. After 4  A4 prints the ink is shown as 70% left. Is this normal 
usage? I'm using under OSX 10.3.3 with the 2.3.7 driver. I've got some night 
shots to print tomorrow, I hate to think how all that extra black will eat into the 
remaining ink.

Steve Bell