The reliability of a vehicle is decreased by unnecessary preventative
maintenance.  That is because every time someone touches a bolt or plug,
the chance of causing a problem is there.  Things can be bent, moved,
left too loose or too tight, etc.  That is why people that work on their
own vehicles usually spend quite a bit of time doing it.  I have only
manufacturer recommended maintenance done by the dealer and seldom have
any problems at all.

Depending upon the metals and plastics used in the cooling system, the
coolant can be optimized.  If you use the wrong coolant you actually
shorten the life of the vehicle.  Using only dealer added Volvo coolant
I have never had to add antifreeze between scheduled maintenance.

The tranny fluid is specific for the aw50-55 5 speed AT. Its spec is jws3309
and it is designed to go 100,000+ miles under normal operating conditions.
You might want to replace it sooner, but be sure to use Volvo ATF for this
vehicle or an equivalent, e.g. Mobil 3309, Toyota Type IV, etc. Do not use
anything else, the ATF is formulated specifically for the friction compounds
in the transmission and for an extended drain interval.

The antifreeze is similar, it is an extended change interval coolant;
100-120K miles or something like that. Most OEMs are going in that
direction.

If you want more on this, search the forums at www.swedespeed.com or
www.volvoxc.com/forums/. There has been a lot written. The coolant is
debatable, but there is only one answer for ATF: JWS3309.  It is not your
run of the mill atf.

PS