Actual and base version. Add new info?

Alexey,

if you want to be able to compare current schedule withh the baseline both shall be updated. In other case you will not be able to apply Erned Value Analysis and track activity performance against the baseline.

But you can apply other methods of project performance analysis. I may suggest to assign target dates and target costs to the project phases and just analyze if your targets were achieved. In this case the baseline is just a set of target dates and costs and in this case it is not necessary to update it when more detailed information becomes available. You still will be able to compare planned and actual dates and costs with the approved targets, analyze trends and risks, manage project buffers.

Best Regards,

Vladimir