In theory, they can live with kidney failure for years as long as it is being well managed, but equally, some cats don’t respond or accept things so may only have months, I’ve had both ends of the spectrum. It certainly isn’t called an emotional rollercoaster for nothing. Lucy has had early stage for 2.5 years now, she has only had a diet change, with no medication, but we can’t put her on a fully renal diet, so hers is a mixture of renal, senior and adult. Tilly might surprise you diet wise, I’ve had very few refuse to eat biscuits, and Lucy was on 50g pouches as she wouldn’t eat 100g ones, but yet will happily eat renal food! I also started with one of the RC Palatability packs, she now has 4 different brands of renal wet, including one that also has joint support in. I don’t think you can make any decisions till you know what her current bloods are like, her agility could be age rather than kidney issues.