Grand Theft Auto 5 - Expected Download Times? (PSN store)?

I preordered a copy of GTA 5 on the PSN store the other day, under the assumption that I would be able to preload the game before the 17th. However, with that recent leak going around, it looks rather unlikely that a preload will be possible.

I've never actually downloaded a large PlayStation game from the Store before, so I am entirely clueless as to what download times I should expect for a game such as GTA 5.

I was wondering if any of you would be able to provide me with a somewhat solid answer?

My internet connection download speed is 60 Mbps, and the PS3 is on a wired connection. However, the PS3 is only ever able to download at 5 Mbps.

Based on the speeds that I am getting, how long do you believe it would take me to download an 18GB game from the PSN store?

Thanks.