How often do the freebie sites change, or add, to their offers?
I just saw that another offer has been added to the Canadian freepay sites.
Do they change often? like once a week?
And do all of the networks change their offers in roughly the same time frame?
Well, they change about every 2 weeks (at the least). Usually, big sites (Freepay, OfferCentric, and Trainn) change every 2 weeks. (Not completely, but they may take away an offer or add one.) Small sites (independently owned like Orderit4free, AnyGift4#, etc.) change about every month. Once again, it's only a minor change.
Hope this helps!