Collection + Stampede
With any trasher in the kingdom, this is a 50 VP/turn golden deck.
Technically, you can make this into a Golden Deck without trashing. If there's no handsize/drawing attacks, the 10 Horses you will gain will eventually turn into 15 cards. If those are your starting 10 + 5 copies of Collection, you still get the 50 VP per turn Golden Deck. This will rarely be the optimal strategy, as it prevents you from buying any other non-one-shot card. Being able to play 3-4 (and occassionally 5) Collections and making the rest up with Silver is good enough, especially if you can win the Collections split. On the other hand, in a Collections - Stampeded - Ride - Experement deck, if you open $5/$2, it might we worth trying to grab 5 Collections without buying anything else.
Collection + Stampede
With any trasher in the kingdom, this is a 50 VP/turn golden deck.
If both players do this the game never ends.
Unless one wins the split and gets 6 copies. Then the other person can either resign, or the split winner can run up the score so much (able to score 50 points per turn to their opponent's 40) that the other player can't make it up in 8 turns, and the first player can buy out the Provinces (or whatever). But that would take forever, so the split loser should probably resign.
But if there was a clean split, you are correct.