Mine is now 7 years old and still going strong (hope I haven't jinxed it!). I do periodically put a CTEK on it to keep it topped up. For replacements, I'd go for a Varta from Tayna, using the discount code from Number 27's YouTube channel. https://www.tayna.co.uk/car-batteries/varta/a5/
It'd be cheaper to get a CTEK (or similar) battery maintainer and give your existing one a new lease of life!