Saw that TPG upgraded their $40/month 512Kbps plan to 60GB quota per month (30GB off-peak, 30GB on-peak) from the old 10+15GB/month, so I contacted my ISP (Soul) to upgrade the plan in-line with the TPG plan. Sent it through and all that, so just need to wait for the upgrade.
Unfortunately, this doesn’t fix the speed issues I’m having (Telstra issue?), but hey, free extra quota, so meh. Anyway, the off-peak allowance pretty much means that off-peak traffic is unlimited, as it’s only for 5 hours a day (4am – 9am). That is, if I constantly downloaded for those 5 hours, fully utilising the connection for 31 days a month, I’d have to download at 52.5KB/sec (assuming 30GB = 30 billion bytes). I get around 51-53KB/sec usually anyway, so for all practical purposes, it’s impossible for me to deplete the off-peak quota.