The original offer, part of the After Eight campaign, allowed users free internet access seven days a week between 8pm and 12 midnight and had been due to finish at the end of October, but was extended until the end of the year.
Trinity Mirror has now extended it further to 31 January 2001 and the offer will be reassessed throughout next month.
Following the launch of ic24's unmetered access offer in April, registrations have grown from 200,000 to over 750,000. Trinity Mirror earmarked £150 million for internet investments in March, with £50m of this set aside to subsidise its ic24 unmetered service.
With a number of other ISPs cutting back or even suspending their unmetered packages, Trinity Mirror Digital believes the pace of its service has been the key to its continued expansion.
"We have planned it all very carefully. We didn't offer something we couldn't deliver on," said a spokeswoman for the company. "We have increased slowly, planned very carefully with our telco and we've also had the investment. We've not gone overboard and offered 24/7 free access and then had to withdraw it."
New ventures by Trinity Mirror Digital include the introduction of entertainment site icShowbiz.com this month and the planned launch of general sports and shopping advice sites.
The sports site should debut next month, with the shopping advice site, provisionally titled Choice, launching at a later date.