Yes, "not accessible" means that there's no way to know what's going on "under the hood", unless the manufacturer provides some sort of utility that can do it. The Intel SSD Toolbox, for example, can report (via SMART data) the total number of writes that the drive has sustained, which is a bit of a guide as to how much of it's useful write endurance has been consumed.
But I'm not aware of any manufacturer-supplied software that can provide any more detail than that.
SSDs have spare flash pages to help with their wear leveling algorithms, so you won't "run out of blocks". The worst that will happen is that write performance will get poor if the drive struggles to keep up with the requests. Garbage collection is there to enhance write performance by creating fresh, empty flash pages before they're needed. If those pages aren't available then the drive just shuffles data on the fly to free up pages as the requests come in.
It isn't until you reach end-of-life for the SSD (where it's flash memory is worn out and it won't accept any more writes) where you'll start getting error messages. Unless, of course, there's some other actual physical fault that develops before them.