They have 15 more trains now than they did before displacing R46s on the A/C. How is the spare factor too low? The spare factor was low before the R211s arrived because they retired the last 11 R32 trains early, but they were able to get by. Now they have 15 trains to make up for the 11, with more coming each week. 2 more sets are doing burn in testing, another set was just delivered. I'm assuming too that the new trains are much more reliable. That would lower the need for spares.
I remember back in the 60s as the R32s came in first the triplexes, then the standards all disappeared really fast. I remember railfanning as a kid on the Sea Beach and then changing at 62nd/New Utrect for the West End and an old train came rumbling in, can't remember whether standard or triplex, and that was the last time I saw one on the BMT southern. The standards continued running on the Eastern for another 4 or 5 years until the last of the R9s replaced them. One day you'll have thought all the R46s are gone and one will come rumbling into the station, and the next day you'll read here that it was the last regularly scheduled run.