The ones that come back are ones that do not know the truth about the truth. They still believe what they were taught.
A friend of mine DAd themselves man years ago. Lived a normal life. Got married etc. Was out for 18 years at least. Her family "spiritual giants" shunned her for 18 years! Now back in she posts things on Facebook about how wonderful and supportive her parents are to her and how unconditional their love is. Ugh!
Just recently I talked to an old friend DFd 10 years ago. Had been an elder. Says he misses it and loved being a JW. He said you can't deny it's the truth!
Unless they are mentally out, there is a good chance they will return.