Running dry can certainly improve insert life if you are doing a lot of intermittent cutting with poor coolant flow.
Coolant, especially thru tool, I would still be inclined to use when lingering over a small area - helical bore milling, for example.
The trick to dry machining is to have a rigid enough set-up to be able to run the insert/tool at the optimum metal removal rate. This will help keep everything from getting too hot.
As I work on large, flimsy castings which can vary in quality, inclusions and hard skin are my main ball-ache so I tend to run with coolant - if all the tips go without warning I seem to have a few more nano-seconds of grace to save the tool body itself...