Jeez...why jeopardize a $~100. motherboard and maybe a
$~150 CPU when a $~6.00 replacement fan can be obtained.
I agree, though for single good fan it can cost over $10
delivered or by the case, less than $1.50 each. Regardless
if there is any question the fan should be replaced.
HOWEVER, there are circustances where simply replacing the
fan is not an option, or at least not so easily done as
written. Some are proprietary shapes or sizes.
The important factor is the quality of the replacement. If
one buys a lower quality sleeve bearing fan, they may have
actually had a better result and longer life by relubing
their current fan than installing a new one.
The primary fan relube scenario would be one where the
system "needs" to keep running, be taken down and back up
with limited downtime. Perhaps downtime in a PC for home
use isn't so significant but for some companies it could be
very costly to allow a fan to fail by delaying until a new
one arrives.
Lubing sleeve-bearing fans is a fact of life though, it's
not really unexpected that it should occur as a regular
service item just as it should be done on any other fans in
your home such as a furnace blower, etc. PC fan is cheaper,
but it's also a lot easier to access and lube.