It's not just time, the convection will also dry things out a lot faster, so turkey, for example might need a foil covering for part of the cooking time.

I find that it varies, depending on what I'm making. I always reduce the temperature by 25 degrees, as suggested by the oven manufacturer, and keep an eye on whatever I'm making (especially yeast and quick breads, which are in the oven for 45 min to an hour). Often, I need to tent to prevent over-browning. I tend to be more mindful, but that's not a bad thing . . . ;o)

I've found it to be about 10 min faster for tarts & cakes.