The pre-eminent set collectors at the trade days always sets up in the same corner One always has the same box of Topps, Bowman and Upper Deck dupes, plus a full 5000 count box of inserts from the 90's. He buys multiple boxes at a time and makes up sets, then leaves the dupes for us to peruse. The other has many grandchildren, so he makes sets upon sets for them all. He is currently working on his 10th base set of this year's Topps! Fortunately for me, he gets lots of doubles of the inserts, and even some short print doubles.
Lately, the former has been going through my box of '70's dupes, and he has picked out over bv200 in cards, so I am able to pick and choose what I need from him, but he has only a limited number of inserts to trade. The latter is indebted to the former for near bv400 for helping to finish all those base sets of Topps. So when I need inserts for Series 2 Topps, I go to the second guy, and whittle down what he owes to the first guy by relieving him of many of his insert doubles.
In addition, a newer guy to the Trade Days busted six or seven boxes of Series 2 and had hundreds of inserts to trade. He was looking for the autos and relics only, and was trading everything else. That's where some of the Sweet Spot autographs I have pulled and cut-rate autos I have traded for or bought come in handy. I was able to get most of what I needed for S2 inserts, about 80-90 cards, from him for a Billingsley Sweet Spot auto, an Ethier A&G auto, a Jordan minor league card, and one other low-end auto. Not bad!
As you can see from my wantlists, I am down to only a dozen or so insert cards left for Series 2. That is one of the great things about Trade Days. I can rely on my trading partners to help me finish some of these sets.