Don't know of adjusting timing for it(cm has hat option inbuilt we don't

) but u may be keep them always on or always off.
Give a try to Screen Filter app from market.
Try following on your own risk,I haven't tested it but it should work fine.
If u want to keep them always on/off then u need to modify a file in /sys/class/leds/keyboard-backlight/brightness. open this brightness file in texteditor n put 255 to always on or 0 (zero) for always off. save the file n change permissions to read only.(U need to be smart to do this cause if u tap on softkey meanwhile before changing permissions.)
OR u can directly change permission to r--r--r-- when softkey lights are off.this will make them off always.n same can be done when they are lighted up to keep them on always.
I will also try n let u know but till then u are on ur own responsibility.
EDIT:
I just checked it n it's working.
Now I will find something to adjust the timing,it will be better,right?