I typically keep moving left with the same ball until either 1 ) I stop carrying or 2) I can see the ball path start to change (starting to hook early...  or more recently not reacting due to plastic straight ball carry down).  This is where knowing your arsenal and expected reaction becomes critical.

I agree with Strapper.  As long as you have good reaction and carry, follow the shot until you don't (if that happens). 

The key is to watch your ball reaction more and more closely as you move in.  If it starts to labor because maybe the ball is finding friction too early, then often a weaker cover ball is a great option. 

Much will depend on proper surface prep and your ball rotation.  Guys with lots of forward roll sometimes struggle when the lanes have opened up a lot because they start to lose the amount of skid and rotation necessary to help with carry as the lanes dry out.  Hope this makes sense.
 

Makes sense to me.  That's exactly where my AMF Heist Pearl with a MOtion hole comes in.  The core and drilling adequately compensate for my lack of hand but that smooth cover (at 4000 lightly polished) guarantees it will not over-react to friction.

The Fusion (With it's lower RG and diff) may not be enough ball to go super around the corner for you. The Hyroad Pearl is a good step down to get it around the corner, because it's higher RG higher diff. Pearl + higher RG and Diff means the world when the ball in your hand isn't making the turn. Example. I bowled with my Network (Low RG high diff) on a house shot this weekend. As the lanes transitioned, I really didn't like the carry from the angle I was at. Threw my friends Dirty Look (Higher RG same diff, weaker pearl cover) and it pushed and turned where my lower RG ball was not working as well as I would hope.