Should Bernie drop out?

Bernie Sanders is currently hospitalized after having emergency cardiovascular surgery. His campaign says he will be at the next debate, but some have called for him to drop out due to health AND his age. (He's 77)

1) Should he discontinue based on health complications or Age?

2) If he should for age, should Biden also drop out? He is 76 and some have questions about his senility

3) Does age matter at all when considering the ability to fulfill elected office duties?