I realize this is an old post. Ridgway was interrogated and high on a short list of suspects long before he was caught. They kept coming back to him, he was hard to completely exclude. What stops a serial killer? My theory is a common one, death and being locked up are the most likely.
My other pet theories are either they move (possibly in the JTR case) or become scared-straight. Look at the gap in the BTK case, he took a very long siesta between sprees. His ego and arrogance was his undoing. Rader and Bundy were cool, intelligent and calculating killers, something shared by LISK. Ridgway was not bright, DNA was what got him.
The LISK killer has probably became scared-straight. Chances are good that he will be active again, the SK thing carries a strong compulsion.
Some collect trinkets or momentos from their victims in the way you would save a post card from a vacation, or buy a key ring that reminds you of a far-off place. In normal people, this carries them to the next vacation. For a SK, the killing is their vacation.
Ridgway and Rader kept things from their victims. Rader had a secret room in his house. Dahmer saved human parts in his freezer. Brudos kept shoes from his victims. Is this a trait of our own LISK? Some save one thing, some save a lot. Some that have saved a lot over the years can give a run down of who each item came from.