Long time biker here - I don't bother with the whole chain rotating nonsense, wear the whole lot out together and replace it. Nothing worse than putting a new chain on a partly worn cassette only to have engagement issues, (despite diligantly observing chain wear according to the dinky chain wear indicator tool).
The key is finding the right cassette/chain at a reasonable price and learning to do the swapout yourself. My ebike has 3000km on the first chain/cassette and it will probably last another 1000-2000km.
NB/ I can make a new chain slip on a new cassette in the small cogs on a normal bike, and it's very easy on an ebike with a motor, so you have to avoid starting off in a high gear or hammering up hills in the wee cogs, there's not enough chain wrap to sustain the load.
The key is finding the right cassette/chain at a reasonable price and learning to do the swapout yourself. My ebike has 3000km on the first chain/cassette and it will probably last another 1000-2000km.
NB/ I can make a new chain slip on a new cassette in the small cogs on a normal bike, and it's very easy on an ebike with a motor, so you have to avoid starting off in a high gear or hammering up hills in the wee cogs, there's not enough chain wrap to sustain the load.