These would not, in the beginning, be viable. A living cell is under a lot of functional constraints, ingestion, excretion, the utililization of incoming molecules, and successful division. And that first prokaryote went out and conquered the pit. And its descendents went out and spread life throughout the world. Not very long at all.
Chemical reactions happen very rapidly.
The autocatalytic set phase transition was probably on the order of minutes. The bulk of the time was probably spent in the evolution from proto-prokaryote to prokaryote and that only because the increasing stability induced by reliable heredity would slow down chemical evolution. And that's what I think happened. This page was last updated june 3, 1998.