I'm in the same boat. I was asked recently to develop a small custom app for a library that would need to be maintained for decades. This left me scratching my head as to which GUI technology to choose to minimize the danger of it being broken/unsupported after 10 years. Paradoxically, I think Win32 might be the safest choice as MS can't really innovate (=break) too much here anymore (although I might underappreciate their skills in this regard).