I have no values but in general PTFE is a soft material and I expect high creep. Probably not a great choice for a seal. Filled PTFE should have much lower creep though.
One small comment. Be careful when looking for data on "Teflon". DuPont uses that tradename for 3 or 4 totally different polymers. You probably need data for PFTE.
be careful with using some of those 'published' values; as Demon3 indicated in his first response they may not all refer to the same thing. What's to stop you from actaully getting your seal tested? I know there's lots of great labs out there (e.g. Axel) that would be happy to do a creep test (short term or long term) on a (Teflon) seal!
I did some rough "memory" tests on square profile PTFE lengths we use as seals. At temperature (100`C+), these seals were clamped up in a circle overnight, they retained the new shape reasonably well.
Don't know if you need to take this into account??