For context on ‘when is the next mirror likely’, here are the last several mirror dates:
2021-02-15
2020-10-02
2020-06-26
2020-03-27
2019-12-17
2019-09-17
2019-06-03
2019-03-21
So it has pretty consistently been every 3-4 months for the last two years - roughly once a quarter, but the end of 2020 into start of 2021 had a longer span between mirrors than prior updates.