I have a few suggestions for games that go that long and you have extra money:

1. After 60 min new items and recipes are unlocked (like delux items 10 000 gold price)

2. Players can buy extra slots in inventory for their money

3. New creep is unlocked that randomly spawns on the map and attacks heroes (a dragon that steals ur items)

4. You can buy a special tp scroll that teleports you to the underground level. There is a maze with monsters and a boss fight in the middle of the maze for extra loot

5. Because support spells, except for ulti, deal small damage in ultra late game make an item after 60 min that converts those spells to deal fix dmg plus percentage of enemy heroes total hp

6. After 90 min heroes start deleveling due to old age