I'd argue adding is the right calculation in many situations, since in most cases you wouldn't receive the benefits of the next risk if you die the first time.

I'd argue adding is the right calculation in many situations, since in most cases you wouldn't receive the benefits of the next risk if you die the first time. So for example, if working in a coal mine is 10 micromorts per work day, and you choose to do it each day, it seems pretty reasonable to call that 10 * 5 days * 50 work weeks = 2500 micromorts per year. You're "paying" that cost each time you decide to go to work, and if you decide to work next year it won't somehow "cost" less micromorts – the possible yous who died last year won't be around to make the decision.