1) wearing chain link parts increase tolerances, allowing chain links to be pulled more away from eachother.
2) upon engaging, the rollers then wear out faster the trailing edges of the chainring teeth, making these look like shark fins.
3) upon disenganging, the rollers have to climb over the hooks, wearing out the teeth also from the created 'under'side, aggravating the shark fin profile. Until the hook is weakened enough to break it off.
The idea behind rotating chains is that a new chain causes minimal further sprocket wear since the teeth material that gradually (during new chain links wearing) would have gotten "in the way" has already been removed by the previous chain.
At some point, a chain just breaks off the remainder of the sprocket teeth / skips over,
The key to keep the sprockets in use is to replace the chain before they weakened that much.
The major wear share origins from the sharkfin shape.
Solution is to flip sprockets if possible, and if not, use a file to remove the hook that the rollers have to overcome to disengage.
With these doings you end up with sprockets that allow a next new chain to complete its entire wearing life (max lengh) with minimal further sprockets wear.
The remaining wear that then takes place is in the middle of the wide valleys between the teeth, downwards towards the center of the sprockets.
This decreases the distance that the chain rotates over, so you lose a part of your tensioners or derailers range, the new chain position starts further, which in turn forces replacement with less worn chain.
That chain could be used further with later replaced sprockets, from the moment that the teeth edges got worn away, and the downwards/to center wear starts. If you don't want to bother, gain of not replacing sprockets will come at a cost of more chains.
Such a regime I used for the front ring since that is the one with the most available material to wear off / distributed more.
The win is a chainring that was mounted early 2019, still is in service, and has withstanded 5 replacement chains.
One teeth broke off likely due to my frame failure (connection bottom bracket - drive side rear wheel broke > half cross section) that caused the chain to pull more sideways / chainline off.
Since a rings price (60) is 3 times the chain price (20), it saved quite some bucks.
In 2021 I bought a stock chainrings but didn't need any of them so far, because I didn't know at the time that the teeth edges nearly cease to wear and instead the valleys wear deeper - from low u to high U.
The Velosolo rings are 4 mm thick, so the "deeper", the closer to that 4 mm, and thus, more surface to spread wear over = less further depth wear.
Replacing chain every 200 or 300 km, for one that does everyday 50 that's like every week, is that worth the hassle?
I'd say file off the hooks, it's a minute work, nothing has to be dismounted.
