yes it will definitely reduce the life of the starter BUT the cars equipped with stop/start have a more heavy duty starter. When the concept was first introduced OEMs did a lot of testing on various starters and I say some starters melt within 30k miles but the supplier kept beefing up the starter. I personal hate the stop/start concept and never use it.
They really need to supply people with a way to more easily avoid this feature. My suggestion would be to simply have the vehicle stay in whatever drive mode was last selected. That way, people could leave it in "Dynamic" or "Individual" all the time. Combine this with driver profiles, and it would be ideal.
When BMW came up with this idea for their efficient dynamics spiel, we had this conversation and the common thing thrown around was "You should be fine with the starter, as it designed to spec and use." However what this spec was was never specified. Fast forward to the present, not many threads about failing starters.
To be honest, you`ll be fine at least till warranty. At about 100k ehh most cars are prone to starter failure anyways.