I love making fruit crisps and crumbles (full disclosure: I have no idea what the differences are between them) all year round with whatever fruits are in season.
They always come out delicious when fresh, and the streusel toppings (again, I don't know what makes something a streusel rather than a crisp or crumble) are nice and crispy and browned.
However, if I make them ahead to time, to bring to someone's house, or to serve hours later, the topping inevitable becomes soft and soggy.
Is there anything to be done? If reheating would help, how long would it need to be in the oven and at what temperature?