North Kyushu Rail Pass - validity/price hike

Hello folks:

I am planning to visit North Kyushu outside Fukuoka for 3 days during Nov 22-26. So, I will need a 3-day N Kyushu Rail Pass. I understand that there is a price hike on Oct 1, 2023 for all rail passes. I just wonder, if I buy the pass at the current price on Sep 29 (and validate it on Oct 29), can I still use it during my travel dates?

I know that for the all-country version, buying from travel agencies allows travelers 3 months to validate the pass. However, the N Kyushu version of the JR Kyushu pass is only available on the JR Kyushu website, correct me if I am wrong. The JR Kyushu website does not state how late one can validate this pass and how much time from the validation date one has to begin to use it.

I know that the price hike is modest, but the worst part is that, after Sep 30, there will be surcharges for Yufuin No Mori. So, with the new pass, I wouldn't be able to just "hop on" this special train, and this is a big inconvenience.

Thank you for your help.

Sep 29: you will buy north kyushu pass
Oct 29: you can activate it
You dont need to pay extra fare