IMHO: A few hundred miles maximum then change it; less is OK. The cam break-in is pretty much done in the break-in period, but you want to maintain the ZDDP to at least the 1200-1300 PPM range, which was the old standard.
FWIW: Looking at the Lucas oil data sheets, the ZDDP is 2100 ppm. That is for sure much higher than was in the oils before the ZDDP reductions started occurring, so is more than plenty. Some testing shows that the higher levels than that (like over 2500 ppm) can cause new problems to crop up in wear surfaces. So I would not recommend Lucas AND a ZDDP additive; you going to ending up with ZDDP levels approaching or exceeding 3000 ppm. Might be A-OK for break-in.. the research that I have read does not address that per se.
One thing I do not like about the Lucas oil is that they say it uses a paraffin base oil. Quaker State and Pennzoil had quite a run of crappy oil in the 60's-70' that was notorious for causing high levels of sludge and deposits in engines, and that was due largely to the paraffin base oil. That might be different now, but it raises a question in my mind. It carries no API rating.... that might be bad, or that might be good!