Previous thread here for background and some excellent advice for anyone else who needs it.
PolterCat has remained on Loxicom and the difference has been remarkable, he's been a complete pain in the arse TBH, running around and jumping on things like a cat half his age.
Saw the vet today for a check up and to talk through options and agreed that, although there's a possible risk to his kidneys, he's in good health (and has lost 250g as a result of all his running around), and quality of life and removal of pain is most important, so we'll keep him on Loxicom and consider blood tests at his next check up in 6 months.
I'm thinking that even if he did get kidney disease (which is a risk in older cats anyway I think?) we'd still need to medicate his pain and the Loxicom is so effective and easy for him that I would choose quality over quantity of life every time.
What I'm pondering is whether I should make any dietary changes to help support his kidneys. I know there are renal support foods, are they worth it? He currently has a mix of wet and dry but has always been a good drinker and still is.