Well... clearly, Changelings can die.
Clearly, they are not as powerful as the Q, because I can't imagine that even a barrage of Klingon phasers (cf Apocalypse Rising) could kill a Q.
Clearly, they have much longevity (cf Children of Time)
However, how long they live and whether it is possible for them to die simply by being alive too long is not explored in much detail. So the most accurate answer in this case would be something along the lines of "I don't know."
When in doubt, hug your teddy.