Advice on Direct Drive Turbo - new cassette or current bike cassette

Just buy another cassette for your turbo and stop thinking about it

I'm using 8 speed on my turbo bike on a Kickr2 turbo, all works OK. And since I mostly use erg mode I don't really have to change gear, so stay in the gear that runs best anyway.

For the price of a new Chorus cassette and chain I'd just buy a shit box bike (see <£300 bike review on road.cc) and just make the geometry and contact points the same as my summer bikes.

There you go, bosh a bike you can just train on rust the headset solid and not worry about any fatigue to your nice bikes, plus there's no hassle messing around with cassettes and you know each time you do you'll have to re index it.

That's what I'd do anyway

I've been wondering about this. Most people I know use a turbo wheel, so a turbo cassette isn't much different.

The simple solution is to change your chain regularly so the cassette doesn't get worn. I try to do this after every 1000k-ish, and confirm with a chain tool that the stretch is still a way under 0.75 - some chains last less miles than others. 

So, IMO your best bet is to buy a chain tool and keep an eye on wear so you can change your chain before it gets too worn. Whether this is on the road or not.

I'm using a DD turbo and I use a separate cassete on this as to my curent cassette.  Its a lot less hassle and you only have to do the dirty job of changing the cassette once (not before and after every session) and its seems to fine.

If your chain hasnt worn then either option should work.

If you use the chain after its stretched then yeah your cassette wears too.

I don't use a turbo but by that logic are they advocating replacing your cassette every time you replace your chain?   Doesn't seem to make sense.