Continue to cook the sirloin roast until a meat thermometer registers 130 degrees at the CENTER of the roast for medium rare at the center, medium on the ends. This should take around 20 â 30 minutes per pound, but never rely on exact times. Use a meat thermometer instead.
Storage: Keep the box because unused phyllo dough can be refrigerated or refrozen. You can wrap any leftover phyllo tightly with plastic wrap, place in its original box and keep in the refrigerator for up to 2 weeks. For longer storage of up to 2 - 4 months, refreeze phyllo.
She mentions that the dough can be kept in the fridge for up to 36 hours (but it needs to be put there immediately after mixing). I have gone for the full 36 hours once, with great results. I did keep it in the coldest part of the fridge (near the freezer wall, in the back of the fridge). It did take over 8 hours to ferment, once it came out.