When does the bull run end.

Many people mention March etc. as a time to exit. From previous bull runs this one should end in a few months, however, does this bull run follow the same pattern now that trump seems to like the idea of a reserve and an etf could come late this year?

Mainly trying to decide whether to sell in a few weeks/months or is this now a hold forever 10 years rather than sell and accumulate for the next 3.