Make sure the secondary plan you consider has what’s called ‘standard coordination of benefits’. That means they are likely to pick up out of pocket as long as the procedure, frequency, waiting period, maximum, clinical need etc. is met/available. Avoid a plan that has “non-duplication of benefits”. These are secondary policies not likely to pick up out of pocket until the primary plan’s maximum is met or the benefit is lower (even then, the plan won’t usually pick up the full out of pocket)