Boge carto break-in? When to change?

[footbag]

I have some Boge Cartos with an AGR tank. After about 5 days, they tend to get a muted flavor. I figure this means it's time to replace them. But, when I replace one, it has a bad taste for the first day or so. I'm pretty sure I'm filling them adequately, but the flavor seems to be coming from the carto itself. Is this just something Ill have to deal with or is there a workaround?