10 years is a long time. Over its lifetime, Apple has changed the Mac's CPU architecture every 10 years. (They've been on Intel for 11 years now, the longest of any, but there's been rumors of another migration for a couple years now.) Needing to support Mac software for 10 years, then, means supporting your users through an architecture change.
There's probably not much platform-specific code in a password manager, but what are the odds it'll work perfectly under their next emulator, or that you can take such an old codebase and just recompile? 10 years ago, the old "pbproj" format was still supported, but the last Xcode that could open them was Xcode 3 (requires OS X 10.5 or 10.6).
Less than 10 years passed between the last Apple IIe sold by Apple and the first PowerMac G5. Or the last Newton to the first iPhone. Or the original Apple I to the Macintosh II. That timescale has big generational changes, and I don't agree that it's realistic for third-party developers to support software that long at no extra cost.
There's probably not much platform-specific code in a password manager, but what are the odds it'll work perfectly under their next emulator, or that you can take such an old codebase and just recompile? 10 years ago, the old "pbproj" format was still supported, but the last Xcode that could open them was Xcode 3 (requires OS X 10.5 or 10.6).
Less than 10 years passed between the last Apple IIe sold by Apple and the first PowerMac G5. Or the last Newton to the first iPhone. Or the original Apple I to the Macintosh II. That timescale has big generational changes, and I don't agree that it's realistic for third-party developers to support software that long at no extra cost.