First of all, it cannot be emphasized this enough, your license to use SPAD.neXt will never expire, and you can always use it, once you purchased a license.
For always being up-to-date and being able to use the latest version of SPAD.neXt, you will need a valid update subscription. Once it expires it's your free decision to renew it or not.
If you do not renew it, you will "just" stay at the major release, that was published when the subscription expired. If you decide to renew the subscription later on you can do so.
What will be charged for the update subscription?
The pricing for the update subscription has been determined as follows (Dec. 2018):
All prices +VAT.
Normal License (any Standard license)
(Also keep in mind, your first year is always included in the license)
Do I need to renew the update subscription even with the Complete licence?
Yes. The complete license is just "the complete package" (everything that's there featurewise and will ever be there in future). Nevertheless coding new stuff costs time (and thus money). The update subscriptions is to upkeep the development. Just like e.g P3D. Just that we openly say why, and not just say "Hey, if I change the major version, go and buy a new license, and I change it every year"
If I have more than one licence (or addons) will i need multiple update subscriptions?
No, one update subscription will be accounted towards all your licenses.
Just renew the update subscription on one of your licenses, and open a ticket with the additioal ordernumber(s) to account it to as well.