Yes, you can export all of your data at any time, and for your complete peace of mind we would encourage that you do so regularly, e.g. at the end of each month. Affinity enables export of account data, in CSV format, via the Admin menu at any time. That data should then ideally be backed up locally within your own organisation as part of your standard data backup processes.
But, be aware that exports are for your own use and are independent of any software system. They will most likely not be able to be imported directly into another system with some work from a developer, but at least you have a full useful copy of all your data.