I don’t want to switch to discord.js v13, do I mind staying in v12? Discord v12
Updating is highly recommended as discord.js v13 includes many new features, such as thread support and interactions. I’m not sure if you are aware of this yet but Discord recently announced that verified bots will no longer be able to use the message event unless whitelisted starting fall next year, which means if you are ever planning on growing your bot above 100 guilds you will need to switch to slash commands, which is only available in v13.
Also note that v12 is deprecated, which means that if there is a breaking bug, the discord.js team will not update older versions as they can only release new versions. It only takes one Discord feature for something to potentially break in older versions, and with threads releasing to everyone who hasn’t enabled it early soon, you won’t want your bot to break in every thread channel.
Creating a bot includes maintaining it, and even though discord.js updates may seem like a pain to support, it’s something that you’ll need to do frequently.