Yes, it sounds like you'd better check the length of the brushes. No other car problem has come close to providing the list of on road emergencies that charging failures have. Best add a voltmeter too.

When you check the brushes, use a light and a fingertip to gauge the wear in the slip rings. That would be your best gauge of whether you are close to needing a rebuild of the alternator. If your suppliers provide the sort of on the shelf rebuilds our US suppliers do (e.g. Autozone, Advance, O'Reilly, NAPA, etc.) you should look for a local rebuilder or do your own bearings and maybe slip rings.

But mostly, I think, under 500K KM, brushes are the only thing you'll need.

Depending on the year of your 240, the intermittent charging could be a crusty fuse, but I seem to remember your Polar is beyond the fuse years. It should be if you have an electronic speedometer.
--
Art Benstein near Baltimore

Ever stop to think and forget to start again?