DCA is not an S5 base, its an RW base. I'd guess 2-3 months at DCA for reserve. PHL, DCA, PIT, IND, DEN, and (soon to be) CMH are the RW bases. ATL, ORD, IND, and CMH are the S5 bases.

Reserve would be 0-1 months at PHL or CMH right now. PHL will probably be staffed in the next 3 months and except for the top 5 or so, its pretty junior. At least through 20 are staying put till upgrade most likely, so it'll probably stagnate in the next 3-6 months. CMH is going to be the place to be if you want to get high up the FO list quickly since no one seems to want to go there.