The 10% premium for fixed weeks is based on the
cost of the week the year the resort opened. So changes in
point charts will affect the cost of the week you purchase. FWs are
especially beneficial if you are looking for a week during Fall Frenzy or Spring Break.
For example, I purchased FWs at CCV in Studios for week 44 (special runDisney Food & Wine week), week 47 (Thanksgiving most years) and week 48 (first week of holiday season). Each of these weeks cost 118 points to purchase, which was a 10% premium when CCV opened (as those weeks cost 107 points then). In 2022, those same weeks cost 115, 126, and 121 respectively. If I were to use all 3 in 2022, I would "save" 8 points (and only pay a premium of 3 points instead of 11 points on my week 44). If I cancel, however, I only get back the points the FW cost me (118).
The CCV RunDisney events, btw, correspond with the runDisney races, and give special benefits for those races, such as advanced registration. Additionally, they are the ONLY FW that can move its check-in date, which is one reason we got it.
I was tempted to buy Week 48 at RIV, which would have cost 120 points for a Standard Studio to buy the FW, but is 116 to book (so the premium is only 4 points) or Week 52 at RIV, which is 196 points to buy but 209 points to book in 2022.
I highly recommend this thread from a while back on the benefits of FWs:
https://www.disboards.com/threads/all-about-fixed-weeks-riv-ccv-aul-vgf-poly-charts.3806985/