Have you log into your my virgin media & checked your bill(s)? Click on your latest bill, then click on package, then looked at the promotional offer(s)? If you have any loyalty discounts it will show there & state when they come to an end.
I don't know of anyone with a permanent loyalty discount. Mine was only for 18 months after negotiating a deal with them, each bill stated the expiry date of the discount.
You can always phone them up & renegotiate a deal & ask for another discount though don't expect them to hand you a discount for nothing.