The trade down decision has to be counter balanced with who else has the top ten picks and what players do they want. If we want a QB, what do the other teams want? A top LB, DL , LT available? We might be able to trade down 3 places, get a top QB or LT position and pick up another low 1st or top 2nd pick to get a DL or top LB.
It all comes down to how you can maximize the trade, and get multiple top picks of top needs.