DTW is just a quantum leap ahead of MEM as far as comfort and choice of lines etc. Reserve is reserve, but I would much rather be on reserve in DTW than in MEM.

I would expect 2-3 months of "reserve", not because you can't hold a line, but due to the number of IOE trips and green lines that prevent you from holding one. Build-up lines are a good choice if you are on reserve, since they are running about 50-100% trips. You will fly on reserve though, so there won't be a lot of sitting around.