You're forgetting they'd have a bunch more 9 year customers with this discount structure. Edit: Sorry for being direct? Let me be more cautious: It's plausibl

You're forgetting they'd have a bunch more 9 year customers with this discount structure. Edit: Sorry for being direct? Let me be more cautious: It's plausible that, under the proposed pricing regime, the 9 year retention rate for customers would rise more than enough to offset the higher margins enjoyed today at the current retention rate.