I have picked the next monster that the party is going to face. It looks quite challenging to me--I would have estimated it at a higher CR than the Monster Manual gives it. I'm a little worried about what it will do to the party.
However, I have decided to trust my players. They have handled with ease everything I've thrown at them, so I'm sure that they'll find a way to handle this one.
But I still find myself thinking about contingency plans in case they die. I usually find the easy access to resurrection a wart in D&D--but it does mean that there's a margin of safety for the campaign when there's not enough of a margin for the characters.