How does the scrap value affect the useful life of an equipment?

How does the scrap value affect the useful life of an equipment?
It is more likely to be the other way round! If an item of equipment is going to be disposed of by a company, and if the item still has a good useful life to another owner, the scrap value will be higher than the scrap value of a similar piece of equipment that is beyond economic repair and use.

This being so, a company has to take a calculated economic view of its equipment. Should they retain it until it is totally worn out, scrap value nil, or should they dispose of it earlier, while it is still in good working order, and thus be able to reduce the overall 'lifetime cost' of the item? Another consideration is the cost of replacement. If the item has to be replaced, will a newer piece of equipment have a greater of lesser 'lifetime cost' than the item being scrapped? Sometimes there is a fine balance to be struck. Other times the calculations show exactly what the right decision would be and exactly when the disposal should be made.