My Volvos specify the timing belt at 90,000. The water pump is driven by the timing belt.
In general, for those cars, timing set (belt, tensioner, idler) at the first change, timing set + water pump at the second. Water pumps are usually good to about 200,000, so, do them at 180,000 when you're in there doing the timing belt...
For those cars, the tensioner is usually what fails. A 90,000 mile timing belt looks great, but will quickly be destroyed if the tensioner fails.
For my Toyota V-6, I always did the entire set. The 3.0 3VZE engine used the water outlet on the manifold as one of the idlers. A complete pain to change that one, the FSM required removal of the intake manifold, in itself a 3 hour job, to get the water outlet changed. I bent a 12mm box wrench to go around the intake. Slow, but a whole lot easier, and fewer parts, than removing the intake.
I hadn't heard that Toyota tensioners were so reliable, but even hearing that, I am happier having done it as a set.
It was a lot of work, and parts aren't that expensive when compared with labor, even my labor. When you balance that with the damage done by failure, I prefer to do the timing set.