Oneiric: Can't reinstall previous purchases

Binary package hint: software-center

If I try to reinstall previous purchases, I get asked to sign into the Software Center, I do, then it brings me to the Previous Purchases list but there are zero items. Though I have purchased several apps.

What's the cross-release story for such apps? Are they automatically provided for each release, or only if/when the publisher decides to make it available for the next release?

If so, some sort of better user feedback about that would be good. Like, "you bought these apps before, but they aren't available for 11.10, sorry" or something. Just so I know Software Center hasn't eaten my apps.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: software-center 4.1.3
ProcVersionSignature: Ubuntu 2.6.39-3.9-generic 2.6.39
Uname: Linux 2.6.39-3-generic i686
Architecture: i386
Date: Wed May 25 10:40:12 2011
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release i386 (20110422)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=en_US:en
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: software-center
UpgradeStatus: No upgrade log present (probably fresh install)