[Avodah] 10 tribes -- exile without redemption

[Ben Waxman via Avodah]

Why was the exile of the 10 Tribes permanent (putting aside any modern 
day claims of people claiming they're descendants)? What did they do 
that was so awful compared to Yehuda and Benyamin (meaning so 
significantly worse that murder, sexual crimes, and avodah tzara)? Yes, 
I know that they broke off but do the navi'im really work to reprimand 
them and get them to go back to accept Davidic rule? It doesn't seem to 
me that the navi'im spoke that much about it.

Or, did they seal their fate the moment they broke off and the time 
before they went into exile was simply waiting time?

Ben