The idea is genuinely interesting and fun :) - but there is a bad balancing issue.
Until about 7 minutes the rate of packages is low, a few tries and it is easy to collect all (obtaining the maximum amount of income to buy things).
Then it starts pouring in. At that point there doesn't seem to be any way to really last much longer (my max was 7:28). Even tried holding and sweeping with belts a bit to keep tossing packages forward before placing them.
The problem isn't the eventual failure, rather that once figuring things out, there seems to be no way for the player to improve, find new strategies to last longer.