3 year. Old Lenovo 3 tablet taking a long time to charge, battery life doesn't last over 12 hours anymore, is it going bad?

Battery probably is going dead no big deal you can get a new battery on eBay for less than $20

Laptop batteries don't last forever. Three years is about all you get. Replacements on the internet are lots cheaper than from the brand name maker.

and 12 hour battery life is darn good… Unless you used to get 18 or more []which i doubt]

Check what takes more juice from battery. Some apps eat a lot of juice.Uninstall them.Reduce brightness. If you do not use bluetooth turn it off.