It personally looks like your tip is in the sweet zone to me... if it's not messing your ferrule up any worse than it already is and the tip is playing good I would hold off until it is absolutely necessary
How much will you pay for such tips since they are in the "sweet zone"?
Edit: After reflecting on the OPs pictures, I don't actually have any tips where the edge is worn down into the pad and the tip diameter is worn to less than the diameter of the pad. I'll have to withdraw my offer. But I bet the OP would sell you his "sweet zone" tip if you really want it.