Before there was DSL, we all used 64k modems to d/l ~1 GB OS X Combos: 1,000,000,000/64,000/60/60=4.34 hours, and 4-5 hours is what a d/l always took.
I seem to remember the standard modem speed topping out at 56k. More importantly, that's kilo
bits, whereas a 1 GB download is giga
bytes. My math says 1,000,000,000/7,000/60/60=39.68 hours.
Before there was DSL, OS X Combos were more on the order of 100 MB (the OS X 10.3.5 Combo weighed in at ~88 MB, for instance), which probably explains why your remembered downloads took 4-5 hours.