End of year bonuses (decided around Dec 1 and paid around Dec 28) are a big part of pay at my employer. Will I stay at my job long enough to get the bonus?

If I give notice that I'm leaving before Dec 28 they will very likely not pay it.

If they decrease my bonus to 50% or less of last year's (e.g. to 0) I will consider that not getting the bonus. This could happen if I'm bad enough at my work.

They can choose any non-negative bonus amount but 95%+ of (people, year) reports that I've found have not decreased from the previous year. Last year I had a guaranteed first year bonus that was relatively normal.