CM proclaims a SH is down if it misses 2x generation_poll_interval (set on the SH)
setting:
server.conf
299 #only valid for mode=master or mode=searchhead$
300 generation_poll_interval = 5$
If you see Search Heads' status "Down", you can try it to increase the number.
60 sec is a good candidate.
server.conf in etc/system/default set it to 5 ( this is default) .spec file is incorrect