IIRC, they did a reunion in Aspen some time after Graham Chapman died - his ashes were kicked over by Terry Gilliam at some point in proceedings. They then planned to do a reunion tour, but Michael Palin had reservations and Terry Gilliam didn't want to do one at all - so it didn't happen.
A thirtieth anniversary show appeared on the BBC, but Eric Idle didn't appear alongside the other Pythons - he wanted nothing to do with the project and had to be persuaded to contribute a monologue. The BBC didn't publicise the programme very well, and many Python fans missed it. The critics panned it as being a rehash of old material (missing the point that it was meant to be just that so that the Python fans the BBC had failed to advertise to would enjoy it). The Pythons then concluded that they probably wouldn't do anything similar again. Which probably means that they will, sometime, if Palin can be spared from making travel programmes.
(all of which is a summary of the last chapter 'The Pythons: The Autobigoraphy by the Pythons')