To ensure best quality and smallest file size optimization the transcoding and processing time of a given source file depends highly on the type of content in the video; For example, a highly dynamic scene, with changing lighting and high level of detail (e.g. nature walk) will achieve different results than a static scene (e.g. talking head) or a scene with low level of details (e.g. text slides).
Rough estimates for a 1gb video upload:
Approx 10-30mins during low demand periods
Approx 1-3 hours during high demand periods