You have to have performance data, for EVERY TAKE OFF, unless OP-SPEC'd/approved otherwise.

Never mind playing the ever present "what if?" game? What if something went wrong? Why did you do something outside SOP's when ALL you had to do was tell ATC you needed a few more minutes for your new numbers?

There may be some exceptions. Again, at a former employer, there was a generic performance book. And naturally, it dictated runway length, take off power requirement, as well as max payload capability, VERY LOW. Basically, it was for an emergency and the plane diverted.

We flew charters into some smaller/more obscure fields. Had to call the Flight Ops engineering people to get the data for those fields.