I have a littmann cardiology 3 I bought in 2010 and the diaphragms wore out in 2019. By that time, they stopped selling official kits for the 3, so I repaired it with an off brand kit and was given a 4 for Christmas. The off brand diaphragm lasted only a couple years. My colleague has had the rubber tubing wear out. They say if you wear a collared shirt it lasts forever hanging on your neck but if it sits on your skin it wears out, and she always wears scrubs.
My first stephoscope lasted about 10 years until the tubing became brittle and started cracking. It's the oil on your skin that does it apparently. It went through a couple diaphragms and I lost an ear piece but used a replacement one.
Fair enough. My medical classmates regularly used stethoscopes that were purchased by their parents for the parents' own studies but I understand there may be differences in build quality.