I’m not sure the offset cost works that way. If I read the below thread correctly (in the faq), the cost is only offset for ‘unused time’. In my perception, that means for example if you bought an annual subscription 9 months before the sale, you can spend the worth of the 3 remaining months on your lifetime subscription.
If what I said is correct, you will only be offset for the rest of the month with a montly subscription. I’m not 100% sure on this, but I’m partially also voicing my doubt to prevent unrealistic expectations by the time of the sale.
Edit: @Seraphim44, just so you know.