What is uptime really?

Uptime 300+ day tell us only that the machine is leaved unmaintained and vulnerable even used
for "nothing" because computer connected to the network is not safe even connected to the
private LAN at these days.
Also statistic without explained methodology is worth nothing because we are not able to
verify the numbers or methodology.
Downtime in general is tightly connected to the TCO (Total Cost of Ownership) because it shows
how much time administrator must sit and work to be able to put the machine up again.
The reason why MS Windows machines has longer downtime it tightly connected to inability to
replace files even they are opened (as Unix is able) and get service up only by restarting
this one service (and not whole computer). Also library (DLL) problem with various versions is
not solved on system level in MS Windows.
Longer time for Debian in compare to other distributions may be related to the fact, that
Debian is late with security updates (as was presented here a year ago or so), does not offer
latest security technologies and thus admin must solve this problem with reinstallation or by
cleaning up the machine (yes, Debian is more "stable"... and more older).
Also do not mix uptime and failover (cluster) as uptime means uptime of one machine and not
uninterrupted reachability of the service (backed by cluster, redundacy, round robin DNS or
something similar).