I have not read about guidelines on replacing a sump pump before it shows signs of wearing out. But to give peace of mind, you might consider digging a second pit and interconnect it with the first pit and put a second sump pump there as a backup. Now you would test both pumps from time to time so if one did break down you would replace it promptly.
The disadvantages of crab apple trees. In summer, the apples are too sour to pick and eat. In winter the birds come and leave dropping all over the place.