waterpump? radiator?

for a rad, it is best to take it to a rad shop and have it flow tested.

for the pump, they become less efficient, and often the seal lets go before other failure - you see the tell tale coolant trickle from the weep hole under the pump.

but i have read of the passages gunking up from neglected systems. ditto for the impeller shaft coming loose on the impeller. but since you have to pull it to check, id just toss a new one on there.

my two cents worth. good luck.

When it start to leak it will be a great sign of something going out.