It takes less than a few months to ruin the economy, especially at the speed bots go. In a couple months we'll already be at the point where stuff like Mythril Ore goes for 1 gil and be available in astronomical quantities. On my server right now 2 retainers have 40 stacks up, same price, probably a bot.

There will always be bots, the response needs to be quick, pilling up names then banning them once after 6 months will do absolutely nothing; it'll be like gil sellers on chat, they'll hack/buy a new account and bot away some more for an other 6 months.