On our upcoming cruise, we booked one non-Princess tour where the return time was 3 hours before the ship sailed. I figured, if we had to, we could walk back to the ship in that timeframe. 😉
For the others, the excursions were much farther away and much longer. To me, it makes sense to book with Princess if you have little leeway for things going wrong. Plus one of them combined two excursions into one and doing that with private tour operators was not possible in the time allotted.
We still have one stop where we haven't booked anything. We are waiting to see what the Princess options are. (For some reason, they aren't available yet.) There is a private tour we may do that we're pretty sure Princess won't have but, again, the tour is over hours before the ship leaves. Hopefully, if we book that one, we won't be sorry. 😄