Vyvanse recreational dose

What dose of Vyvanse do you take recreationally? Also, is there any point in spreading a dose out?

Say if you take 60mg, then wait 4 hours and take another 60mg.

How would that differ from just taking 120 all in the one go?

Also, is there a ceiling? Would a higher dose eventually become useless? And only prolong the high, rather than increase it?