AMEX Hilton: To avoid extending the FN, should I hold off on completing the SUB?

After reading about everyone's various efforts to extend the FN, if I don't have travel plans, should I hold off on completing the SUB?

I opened the card in mid-September, and completing the SUB within 6 months means it would land in mid-March next year. If I don't have travel plans before March next year, since the FN is only awarded upon completing the SUB and is valid for one year from issuance, then I should try to leave a portion of the spending unfinished and not complete the SUB, and spend enough by the end of February?