Recently switched to performing them at he end of the workout - following the Yates routines, or pretty close, as they have always worked for me...been doing them full ROM though.
My strength dropped considerably from 6 plates a side for 3-6 doing them first, to 3/4 plates a side for 8 at the end. Got to say my form is near picture perfect and I'm really controlling the negative since following my new routine. Working back up though, with good results too.