Hmm, didn't she get married? May have had a kid.
I know linking park took about 4 years between meteora and minutes to midnight, in that time they played gigs and festivals pretty much most of the time each year (one year they played 320 days out of 365 days. complete dedication to the gigs) Brought out the road to revolution live album inbetween the minutes to midnight and thousand suns albums. Its just a case of knowing what your favourite band is doing. For the most part i've kept upto date with LP since they made it with hybrid theory back in 2000-2001. going back and hunting down their music from when they where Xero.
Maybe Evanescence has just been touring, had a kid, or creating new songs, had a dead in the family. Or merely lazy :/