You can always use a RW the same way as a write-once - they were originally called "CD-eraseable", I believe - and when using them for small pieces that way, it's better to fill them up and then erase, as the usable life is determined by the part that gets the most use.
So if you erase and write a CD-RW every time, you put two cycles on it every time... if you get 4 multisessioned writes on, then you put two cycles on it for every 4 writes.
Since the quoted lifetime is usually 1000 cycles, I'd suggest retiring the media considerably before that, or verifying the media to get an ideao of it's useful life in your drive - some combinations work very well, others weaken very quickly, 50 cycles or less -if the media and drive don't get on, the first write can be poor and the second unreadable - I had a drive that was incredibly fussy with RW media.
A "modified" Grandfather, Father, Son cycle would be that on Day 1, you use a CD-R, Day 2, you use CD-RW #1, Day 3, you use CD-RW #2, then you go back to The CD-R, and either add a session, or replace/store it.
The original point of the cycle with tapes (eraseable), was that with a set of 3 (or more), you were always writing over the oldest with the new backup, and could step back through the remainder of the set if the newset backup failed.
The weakness of the modified cycle, is that you are still exposed to the possibility that one or both of the CD-RW may let you down.
PS. Surprised you've not seen that abbreviation before... AFAIK = As Far As I Know (implication, don't take this as absolute).