A couple of times I had to conduct effort estimations which contained a number of repetitive tasks. The question was, how long does it take to finish all these tasks. For example, I had to provide estimates how many days it would cost to program an interface between one system interfacing to a couple of other systems to exchange some kind of data (trading products in my particular case). There were many systems involved, and many kind of data types (in my case futures, swaps, bonds, money markets, etc.).
It is common wisdom that you gain experience and become faster by applying the same solution tactics to the same problem. Of course, the effort per problem cannot go to zero or approach zero. There must be a lower limit on how far we can decrease each effort for each task even when we have learned for a long period of time. All this is the topic of learning curves.