How long? ;)

Ok, so I'm dating an EXTREMELY sexy Scorpio (Love, Love, LOVE HIM!). We've been great friends for a long while now, relationship just fell right into place flawlessly over the past few months.
He visits his two young daughters once a month on the West Coast (we're on the East Coast) and has just spent a couple of weeks out there for Thanksgiving. His Cancer ex has not stopped contacting him, reminiscent of times past, how great it was for their family to be together again, etc.
Now, don't get me wrong, the thought has crossed my mind that he may be playing both sides, but he's such a devoted boyfriend. He talks about his kids constantly, and I know how much he enjoys the visits. Never bashes the ex outright (which I appreciate- don't dog your past, it makes you who you are and appreciative of your present) but will say how negative a person she is, moody, etc. He & I have talked about it a few times. I'm not trying to come across as insecure by bringing it up, and I totally respect their past. He says he doesn't do anything to lead her on, he considers them friends & they have kids together. Fine with me.
So, my question I guess is this: How long does it take a Cancer to shake a Scorpio? They didn't have a very steady relationship. Were off and on for 4 years. He kept going back to work things out with the ex but it never worked out. I'm thinking he was trying moreso for the girls' sake then out of love for his ex.
While he could be leading her on (it's always logical to keep that a possibility) is it normal for a Cancer to 'read' into his actions toward the girls, doting on them & being in their lives regularly, as actions toward her, the Cancer? IE, way to a man's heart is through his stomach. Way to a Cancer's heart is through her kids?
Any insight will be most helpful. Thanks in advance! Also posted this on the Scorpio forum.

LOL I responded on the Scorp board

Posted by FireGemgirl
I second Ocean Deep's opinion.Cancers literally never let go.

I never go back once I am done...even though they think I will, I never have. But there are a few that I have held onto from within my heart, even from 20 plus years ago, they still have a special place to me 🙂

Thank you for the insight!

If your Scorpio guy has lost his interest in his ex, it is gone, gone, gone. Once that fire is out, it stays out, no matter how much flirting or attempts at manipulation she pulls.
In fact, all that is probably a huge turnoff to him. I wouldn't worry. Scorpios tend to focus on one person at a time so if he's interested in you, chances are the ex is not an issue at all.