For a lead acid battery, you can buy a no-name battery dirt cheap, or a Motocross brand (made by Yuasa) for around $100 (US), or pay top dollar for Yuasa. I think you need to decide first if you want a “cheap” battery or a more expensive brand battery, then within that group search for the best price.
I personally search the internet for the best price on the Motocross brand. There are certainly cheaper batteries out there, and perhaps possibly even better batteries, but that’s what I do.
I shoot for an 8 year battery life and replace them early only if the battery’s performance deteriorates. Open circuit voltage is a rough indicator of the percent of storage capacity. Hotter climates, however, will see shorter battery life span.