I wouldn't say indefinitely but a very long time - such as in 'lifetime'. It also depends on the quality of engineering and materials chosen initially.
I am particular in taking good care of my arms which are mostly assorted Micro arms and treat them as precision instruments.
One or two arms which passed through didn't quite measure up - the stock arm fitted to a Lenco L-75 and an Alphason (not an HR-100).
"If you don't like my principles, I have others" - Groucho Marx