I haven't seen any references in the books for this yet, but the question has recently come up. Are fetishes and expendable spell foci astrally active all the time or just when in use?
Now that I think about it, are sustaining foci astrally active when not being used to sutain a spell?

I couldn't point you to a reference in a book anywhere, but I'm 99% sure the answer to all three will be no, they're not astrally active when not in use.

Fetishes are never astrally active as far as I know. Expendable foci, like all other foci except anchoring foci, are not astrally active by default. It takes a simple action to activate a focus, and a focus becomes astrally active when it is activated. It takes a free action to deactivate a focus. A focus can only be used when activated.

Foci are only astrally active when activated. Expendable Foci are only activated when they're being used, and Sustaining Foci are only active when they're, well, actively sustaining their spell.

Fetishes are an oddity. You have to bond with them and their astral presence travels with you when you project, but as far as I know they're not considered astrally active in and of themselves.

I'd handle it by saying that the bonding ritual binds the fetish to your own astral form. When you're astrally active, your fetishes are astrally active. When you're not, they're not.

The way I think of fetishes on the astral is based on how I view it. Since the astral shows auras of all currently magical beings and things i would say that while you can see a fetish on an aura, it looks like an "empty bottle" or a shell of its physical form, only when you are casting the linked spell does the mana flow through it and only then does it glow on Astral plane.

Foci are simple, turn on, turn off. Same deal as everyone else says.