Generally Toyota water pumps will whine and make noise before completely seizing. Just listen to your engine and replace when you hear it complaining. Could last you the life of the vehicle!
If it ain't broke, don't fix it... or touch it for that matter!
It's supposed to be changed when the timing belt is changed. I have 154,000 on the factory water pump in my 4Runner. Never changed it. Just check your coolant overflow often. If it gets low and/or you notice coolant around the timing belt cover area, you probably have a leaking water pump. The pump will last a very long time, it's the seal/gasket that goes bad first on the 3.4(usually).
I went 126k miles on my 99 Camry 5SFE. Timing belt was loose and needed to be changed so I also did the water pump while I was at it. Water pump still looked like it had more life in it. No leaks, no noise. I did notice that the shaft in the old pump did not turn as smoothly as the shaft in the new pump.
The AISIN made one on my 1MZ-FE (I don't know if it is the same for your 5SFE) looked brand new when I replaced it with the timing belt at 160,000 miles. Of course, "looked brand new" is subjective, but there were no obvious leaks and the bearing "tightness" seemed quite similar to the new one I installed.
OTOH it wasn't all that much money for a new one, and since I was already changing the timing belt it wasn't that much more work to replace the pump. I also swapped out the camshaft oil seals since they were underneath the inner timing cover.
Oh, and I should state that I did take good care of my cooling system for those 160,000 miles, I used Toyota red coolant (with distilled water) and changed it out every 30,000 miles (2X drain and refill).
Never, I'm embarrassed to say. It was changed at 117K by the dealer. I got the truck at 178K and have not changed it yet.
I'm going to have to do it this year without a doubt. I'll replace the water pump at the same time just to save labor.
The truck doesn't get driven as much anymore as I have a fuel sipper for driving to work every day. However, it did haul about 8 tons of dirt this weekend and a pallet of sod yesterday.