The method 1, further comprising determining a third metric for a third process chamber of a third plurality of process chambers used to perform a third process step of said sequence of interrelated process steps, wherein said third metric indicates a time to a third planned maintenance event for said third process chamber and wherein supply of substrates to said third plurality of process chambers is controlled so as to synchronize said {HEAD ~ third planned maintenance event} with said {TAIL ~ first and second planned maintenance event} 
The method 1 , further comprising determining a third metric for a third process chamber of a third plurality of process chambers used to perform a third process step of said sequence of interrelated process steps , wherein said third metric indicates a time to a third planned maintenance event for said third process chamber and wherein supply of substrates to said third plurality of process chambers is controlled so as to synchronize said { HEAD ~ third planned maintenance event } with said { TAIL ~ first and second planned maintenance event }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL