Conclusion

The best policy is to perform $\frac{N}{e}$ interviews, keeping in mind only the level of the best candidate so far. Then, starting at candidate number $\frac{N}{e}+1$, QuitAndHire on the first candidate which satisfies the requirement of Best So Far. This way the asysmptotic success probability is $\frac{\tau}{N}=\frac{1}{e}$.