Way more important for battery life is the charging rate (again, LFP are more resilient there too). Which wouldn't be an issue for grid use.
The only complicating issue is calendar life of the battery when it is above 80%. Over time a battery loses capacity just because it exists, which I'm calling calendar life. The closer your battery is to 100% the calendar life decreases at a roughly quadratic curve (a battery at 80% has about 1/8 the calendar life loss of one at 100%). AKA you lose 8x more capacity per year at 100% than 80%. Temperature has a similar effect above room temperature or so.
So if your frequent charges keep the battery above 80%, that would reduce calendar life (increase capacity loss per year) on its own. LFP has far greater calendar life than lipo, but also cycle life too, so I think it's just as important to keep your EV at 80% or below, whenever convenient, regardless of chemistry, unless your usage will cause cycle life to end the battery usefulness before calendar life is significant; i.e. multiple full cycles per day. But also at multiple full cycles per day you probably won't spend much time above 80% even when charging to 100%.
Ah, to summarize, I'll repeat my simple advice: I think it's important to keep your EV at 80% or below, whenever convenient.
> I would expect them to get recycled and put back into cars
In that case, you'd also get something in return for not having used those cycles. It's a matter of choice then - do I rent out my battery during use, or do I sell it after 8 years.
> In that case, you'd also get something in return for not having used those cycles. It's a matter of choice then - do I rent out my battery during use, or do I sell it after 8 years.
Yeah, but which is more economical is the salient question.
In fact, the battery management system won't even let you fully charge or discharge the battery for exactly this reason. When it shows 100%, there will still be 1-2 kWh empty and the same for a zero percent charge.
For example, a Toyota Yaris use a tiny (0.7 kWh) lithium ion battery and it gets charged/discharged constantly while breaking/accelerating, but it still last a long time because the charge is kept at about 50%.
Also, I'm not sure what components would wear out in an EV before the battery such that it would total the car out. If the EV batteries in totaled cars can be repurposed for grid use, then great, but I would expect them to get recycled and put back into cars unless strapping them to the grid is cheaper than recycling (seems maybe plausible?).