If you are a non-professional diver, the certification has no expiration date. You can dive all over the world without the need to be affiliated to any club or to have an insurance.
However, if you are a frequent diver, you may want to have a non-professional insurance. This will cover the majority of risks and will also avoid you to pay one-time insurances in those dive centers where it is a requirement by local policy.
My suggestion is to have a look at DAN. The insurance does not require you to be affiliated to any club. You can purchase it directly on the website.
You should separate scuba diving license from insurance coverage.
Generally speaking, non-professional scuba diving licenses don't have an expiration. Once you are certified, you're a diver. The only exceptions are the BLS qualification (for example PADI/EFR, which anyway is a non-scuba diving qualification) and professional levels.
For example, I'm a PADI instructor and I'm required to renew my PADI affiliation every year. But the price I pay is because I'm a PADI member and this is part of the PADI membership agreement. If I don't renew it I'm still a diver, a non-professional diver.
My students, once they are certified, are not required to renew the certification.
As far as I know, it works the same for CMAS. I didn't find any information on CMAS website, but this thread seems to confirm that the certificate expiration exists only for professional levels (such as instructors).
The insurance is a different story. The insurance should be renewed periodically, in general every year. It's important to know that, in general, you don't need an insurance to dive. In some countries the insurance is required for professional levels (such Europe, but not Indonesia), in a few countries or dive centers the insurance is required to dive but this is a local policy.
If you are a frequent diver, my suggestion is to have a non-professional insurance. This will cover the majority of risks and will also avoid you to pay one-time insurances in those dive centers where it is a requirement by local policy.
DAN is by far one of the most used (if not the most) insurances. Depending on where you live, they have both trip or annual insurances. This is the case of US, in Europe they only provide annual insurance.