Android phones, apps and tablets

I've just started the process to move over to Three to get their £15 4G unlimited deal once it rolls out. I ended up doing it in store in my lunch break, my only concern is that the contract is for £25/month with a £10 "rolling discount".

I asked if this "rolling discount" would end after 12 mths and I was promised it would continue for life, just checking that there wont be any nasty surprises in a years time.

Is that the same for anyone who purchased online?

Mrs mespilus & I had 3 contracts for at least 5 years that had a 'rolling' discount.
The 'discount' only ended when we renegotiated our contracts,
and,
the paperwork they sent showed 'a rolling discount',
to get whatever standard plan we are on down to the pricematch we obtained.