Crossword puzzle clue "since then at year end"

Since then, at year-end

Hybrid car that runs a few seconds, then stops, then runs again, then stops again...?

HP tablet released in July 2011, then discontinued six weeks later (then revived later in the year!)

Year after year after year

Beat year after year after year ...

Year-end tradition since 1966

Serena Williams has been its year-end #1 player since 2013

Do this, then that, then this again