Hi Sam,
Under the scenario you describe then that becomes a possibility. You might be right, however I just can't foresee a fund or stock market that never declines.
Even the mild decline we had last year (around 8% or so) would have you investing more last June with Twinvest than you would have in April with most funds.
I think that most funds dropped 15% to 30% during the 2002 bear market.
But, in the scenario you describe then investing the whole amount would be best. In reality I just can't see it happening. I guess I have lived through too many bear markets in my life.
Best regards,
Ray