IBM 6126 895 Op Shaft wear

IBM Selectric II Model 895. Short video showing a worn Operational Shaft around the backup bearing and Shift Bearing. In this case, the wear is worse around the backup support bearing so it's not as serious. But often, the wear will be through the Shift Bearing and if it's bad enough, no amount of cleaning and oiling is going to keep it going for long. The shaft will either need to be replaced, or possibly taken to an engineer to build-up the worn area and then turn it down on a lathe to the correct diameter. You will be able to feel more than slight wear with your finger nail where a ridge will be felt.
However, if the wear is only moderate, and the machine is not getting much use, then you might be happy to strip and clean as required. Maybe every few months, or even a few years. It gets easier after the first few times :-)