You can get a free spare pair of licences or two if you have IN devices. I have one Roger On IN v2 and have licences across three different sets of hearing aids from the same device purchase.
The device works with whichever pair of aids I have.
If you have standard receivers rather than UPs then they are £20 each from connevans in the UK.
Very easy to swap out, I have a spare receiver for each side at all times as it’s quite easy to break a wire if you pull on them by accident.
Had my KS10 batteries replaced by Phonak under warranty, there and back in 72 hours.
New battery lasts about 18 hours and I stream a lot, Roger, BT with work.
I have a backup pair of P50s which also lasts a good 16-17 hours.