Hmm. I was hoping for good news that things had changed for the better :( . I want these files to be on the disk so I don't lose data in the case of failure. A common solution here is to acidify the program, but that is not acceptable from a usability standpoint. I don't want to have the user mess around with swap files and the like. When something goes wrong, I want to seamlessly start up where we left off without the user even knowing that something out of the ordinary happened. A tmpfs will do nothing for this case :)
Maybe what you want to do is to write data every [blocksize] (often 4K but it may depend to some extent on the SSD's internal block size, which unfortunately you may not be able to determine easily) in the file and periodically truncate and start from the beginning. To restart, seek backwards from the end of the file.
Alternatively this may be the point where you try to write stuff to an easily and cheaply replaced thumb drive or SD card.