In a word no. There's no restrictions on off peak usage; it is measured but forms no part of the tarrif.
Remember also that peak hours for A&A are 8am-6pm Mon-Fri (i.e. office hours), unlike most ISPs where peak is evenings and weekends. So for home users, who use very little during the week, being out at work/college/school/whatever, it's effectively an unlimited deal.
-Steve.
--
AAISP Max-2 Standard