From my experience, retention dept will try to `save' on all the freebies if possible....if not,they will give u all they can within their authority. Thus, IT/PC fairs are are good time to recontract as u can quote them which ISP is offering value for money sign ups

. I normally call when my contract has less then one mth left.....tat means if they do not offer a competitive rate...I will jump ship. If u notice, my contract is ending with PC show....thus, got higher bargaining power as I can quote othe ISP offers.....and at the same time the retention dept has more leway since there is a fair going on.
Anyway, squeeze wat u can.....consider, then decide the ISP u want to to with. I never commit to ISP on 1 or 2nd talk......until I'm fully satisfied that package I'm getting is competitive to rival ISPs.
Fyi, my recent encounters with retention dept tells me tat they will try to `save' for co....but if u can wiggle around them...they will give u all they've within the package as per their SOP.