It's mostly as @FeRDNYC wrote. We do not have any lifecycle. There's usually only one stable version of WinSCP available – and sometimes a beta version of future release. And very rarely, when there's a critical security issue and the latest "stable" version is fresh and not-so-stable-yet, we release a hotfix of previous stable version. But that happens once in few years only.

WinSCP 3.4 is indeed 19 years old! Do not use it! Actually, it can hardly be used. It hardly supports any ciphers that modern servers allow.

WinSCP version 3.4 was released in October 2003. I'm pretty sure you can consider it long past EOL.

To my knowledge WinSCP doesn't maintain long-term support versions; each version becomes outdated when the next is released, and fixes aren't backported to older versions. (I'm not the developer, so hopefully they'll correct me if that's wrong, but I've never seen any mention of backported fixes, or updates to older versions.)

Hi. I'm trying to locate lifecycle information for WinSCP versions. Specifically, where can I determine when 3.4 is end-of-life and no new patches will be released? thank you!