Honestly, I have been dealing with Axiom for a couple of years and hanging out on the boards regularly and I have NEVER heard of an upgrade/replacement program.

Axiom allows you to return speakers within a 30 day trial period. Some people upgrade within that trial period but that's it as far as I know.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8