I am also not a lawyer. But I think there are two types of changes to ToS.
One is purely administrative. For example, they might change the methods available to reach for support. For example, they might say that you are no longer able to send a Fax to get support help. Or that their domain name changed.
Second is something that changes the service that you are receiving. For example, when you have bought their product they said "we are offering free support for all owners or our doodad". But then one day they decide that support is now paid option for all existing customers.
So the question is: can ToS changes that changes the service/product that you have already paid for binding without your consent? If they decide to introduce extra protection from class action, requirement for arbitrage, etc. is this just administrative or is it actually changing the service you are receiving by restricting your rights?