Re: > My understanding was that when they became foragers,  their diets were changed. And that leads to a rapid decline in lifespan,  not wing wear? 

Research showed that summer bees die off, regardless whether they forage or not. And the winter bees do not die, even though they are hard at work all winter producing heat with their muscles. It cannot be said, also, that the queen has an easy life, being constantly on the move and producing her own weight in eggs daily. 

So, the length in lifespan is less about toil than it is programmed. Reproductive status evidently is very important. Obviously the queen contributes the most to reproduction, followed by the nurses; the foragers are the least involved. Hence, the lifespan of each of these correlates to this state. 

In fact, queenless workers can live a lot longer than bees with a queen. Probably this is due in part to ovary activation. Also, it appears that foragers can have their lifespan lengthened if they are reverted to nurse bees (this has been done experimentally, by removing the nurse bees from colonies).

Reference:
DNA Methylation in Social Insects: How Epigenetics Can Control Behavior and Longevity
Annu. Rev. Entomol. 2015. 60:23.1–23.18

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