Technically there should not be any kind of buffer limitation, the production and consumption forecasts already run for much longer ahead than the day-ahead prices. The real question is whether Victron allows feeding your own custom prices into the DESS algorithm via VRM-API replacing those they calculate themselves based on general market prices and personal (VRM settings) price formulas. Only if that is possible to begin with, will the question arise for how many hours ahead of the current ~10 to ~36 hour rolling window. I never got round to investigating this, I give it 50-50 chance Victron allows / disallows doing that.
See also: DESS price forecast
TL;DR It’s a business/marketing decision, not a technical issue.