Paid Suibscriptions - just checking the best practice on something.
 

I'm looking to add a pad subscription to our forum, which will be an annual one. Initially, to entice people to sign up, we're going to offer one/two months extra for people signing up before a certain date.

The setting up of that is obviously straight forward and I'll make the subscription length 14 months.

Now come the point where we revert to the 12 months for any further subscriptions, here's where I'm not sure what to do. If I just amend the 14 month subscription to a 12 month one is that then going to change everyone who got 14 months to 12 months? If so then obviously not what I want and I'd then have to set up another subscription for just 12 months that I would then flick into place come the date.

If the latter is the way to do it I obviously will want to make inactive the 14 month subscription so that people can't sign up to that one any more. If I do that will it disable the subscriptions of all those that took out the 14 month option?

Sorry for all the questions - just want to make sure I get it right and not end up with a whole mess in a years time!