Definitely the 2:30 minute mark is about the time you want to shoot for when you're fighting the Adamantoise. I can't recall what my times were when I had 3 Ultimate Weapons and was farming for my last million to get the final upgrades I needed for the weapon and accessory trophy, but I'd say that 2 minutes is probably about where I was.

The summoning method is definitely a lot more reliable early post-game than death, at least from my experience. Summoning will knock out those legs and then you just get to focus on the main body. It also ends up depending on which Adamantoise you fight since there are two types with the only difference being how much HP they have.

It was annoying having 10 traps and not enough money. For costing 2 million in the shop you'd think they'd be worth more than 10k a piece for selling.