MTBF & Embedded Use?

I have heard great things about QNX and am considering using it to upgrade
some of devices. Currently we have “dumb” remote access points that
essentially act like port mapped routers, i.e. a particular port from the
WAN side gets forwarded to a particular IP/Port on the LAN side. I wish to
add intelligence to these devices through the use of an OS like QNX, but I
am having a hard time finding specifics on average uptimes of the kernel
(MTBF) to justify replacing a “never down” firmware. Is there any docs? In
addition, are there any good examples of how to make an embedded QNX system
with process monitoring, so that if our “intelligent” application terminates
it will be auto restarted? thanks - Kevin