Recaulking my shower, but some of it is still in good shape. Can I just caulk partway up the wall and join the old stuff with the new stuff?

http://ift.tt/2kADGiX's a picture of what I'm taking about. The worn caulk was mostly along the shower pan itself, but I also had to peel up some going a few inches up the wall. I know new silicone won't stick to old silicone, so do I just need to pull all of the caulk or can I just lay the new silicone up to the edge of the old silicone? via /r/DIY http://ift.tt/2jMIQJ5