This is what doesn't make sense about the Krogan. Sure, the intent might have been to make them bipedal snapping turtles, BUT.
The reason some turtles live forever is that they don't expend much energy normally. For Krogan, who most definitely expend a LOT of energy, I don't see it making sense to live for a couple thousand years.
Combine this with the way their breeding evolved. A thousand eggs in a clutch. Several clutches per year. This is the survival strategy of something that lives very very short lives and doesn't have the potential to live long lives. Sure, turtles lay a lot of eggs, but the survival rate to maturity is one in a thousand and the turtles don't nest every year.
Krogan, on the other hand, are described (mostly by implication) as being oviviparous. Those 'thousand eggs in a clutch' conflict with 'the piles of babies who never had a chance to live' description. The best way to reconcile this is to say they have eggs which are fertilized inside the female and grow to 'maturity' there before being born. Which, given the sheer numbers involved, imply that baby krogan are *tiny*, we're talking can fit in the palm of your hand tiny. And that just doesn't make sense for a sapient race due to the size of the skull needed to support thought.