Processing time after priority date current

[viva2020]

I filed form I-485(employment based) using the date of filing table more than a year back when the guidance was to use the date of filing to apply for the final stage of the process. 

a) After the priority date becomes current (final action date in visa bulletin later than priority date), is there guidance on what to expect? The processing time in USCIS website is between 7.5 - 29 months to process I-485. Does that mean that there is almost a 2.5 year(worst case) wait after the priority date becomes current?

b) I see some posts where the status changed to case is approved for employment based applications. Can any of you that experienced this provide information on how long it took to reach that status after priority date was current?