My understanding is this, I was interested in going on the V2G trial and made a lot of enquiries, at the time Nissan would only backup the battery warranty on the 30 and 40Kw models, however OVO were in discussion with Nissan to see if they would also honour the warranty on the 24Kw model.
I never followed up to find out what the outcome was as the maths didnt work for me.
As far as degradation goes there was some research that suggested that the extra charging cycles did not have a detrimental effect on the battery SOH, (that is why Nissan supported the warranty ie it wont cost them anything)
I liked the idea but the trial was very restricitve in the hours that the export was being done, I was quoted massive savings but when I analysed the numbers it was complete rubbish, also it was not known at the time what would happen at the end of the trial, yes you get to keep the charger but it is managed by a 3rd party platform (kaluza) I wanted V2H after the trial they could not say if that would be supported, even though the charger is capable of it.