I possibly used it three times and ever since, it never appeared any more. I sincerely don't mind being Silver for the time being because the games I have are oldie and more single player, but for some reason I thought this type of offers would last forever. Then again, paying £12 for 12 months would be a pretty damn cheap discount.
See if it appears on any other silver profiles you have? easy way to findout! I've not been silver for about 3 years now, think i got a 12 month gold for a birthday present, then did some dash offer of 12 months gold for about £22 with a free halo reach avatar item, then did the 1 month for £1 offer 6x times on Xbox.com, then a few more times on the dash by signing a silver account in clicking on the offer, then singing my gold account in. I think they have since fixed that exploit however. Not sure if its worth renewing in January as i hardly play on live now, compared to what i used to.
From time to time it appears on my other Xbox LIVE accounts, but I'm just looking to use my main account. The others only serve to download from other country marketplaces.
This might not help however, I got offers my first year (£1/2 half the time) and then nothing. 5 weeks (and a few days) of waiting and I was becoming feverish, but my xbox no longer loved me :/ Can't help thinking there are 2 tiers of account (an introductory and a normal) and that the offers you receive are seasonal. For example, got worse offers in the run up to Christmas and January but better ones after the summer holidays and in early spring. Have no way of verifying what happens with other people, although would love to find out.