Most probably the NAC ones might go off first.
Notice tat SLBP took in the most number of
B9TL Wrights yet the LO3x gets extended. The extended
LO3x would replace the NAC VO2x on JIS
services by then.
Means JIS services will be fully air con very soon. 
since few years ago.. when SMRT announces it has a full AC
fleet, and with introduction of DBTF.... public been complaining
the presence of NAC buses... so now all condemned to JIE..
SBS tt time already promised and all that.. say the last NAC bus
will disappear by 2012
so.. i dont think they will be extended..
but since this is singapore... high chance prata flipping will be
involved and not many residents will remmeber the 2012
promise..
CCL also opening... so less reasons to procure more buses...
lifespan extension is just to meet the opening of CCL i guess...
paya lebar sector already seen reduced bus loads..
about this lifespan extension of 2 years... its a miracle
commercial vehicles owners arent complaining to LTA.... since comm.
veh lifespan are also capped (20 years).. because they see SBS like
that, they will also demand an extension..
ohh i forgot.. SBS is a GLC afterall 
..
I don't think CCL will be able to handle the future loads if
they keep on increasing population. So bus system is still here to
stay.
I think should be fair to SBST, since SMRT had taken away loads
in CCL, SMRT should give up some bus routes in return to SBST.
