Hello,
What is the supported limit for BGP NSR session, form the link below i see it is 5000 NSR session
http://www.cisco.com/c/en/us/td/docs/routers/asr9000/software/asr9k_r5-1/routing/configuration/guide/b_routing_cg51xasr9k.pdf
However i was able to configure about 6776 sessions with NSR and all sessions were NSR ready...
-Ramdas