visitor visa vs RRVrrv

My wife can only get a 3 month-1 year RRV. Renewed it twice already, but it is a bit pointless doing this indefinitely until such time as she, or more to the point, we, are ready to move back to Australia. But she also needs to visit Australia in the mean time, for which a visitor visa will do if this is possible.

She can get an on-line ETA quite easily.

But does this automatically cancel the PR?

Sorry, I just realised that she is not on the list of eligible countries to apply for an on-line ETA. The DIBP website states that "If you do not hold a passport from any of the above countries or regions, you cannot apply for an ETA online." However it goes on to say that "You might be eligible to apply for an ETA through a travel agent, airline or an Australian visa office". I am guessing that this means certain other countries, such as those on the eVisitor eligibility list. In a previous post, wrussell advised that the "in-person" method will not cancel the PR, but the post has since been deleted. And I wouldn't have the first idea on how to apply for an ETA in person, given that visa service offices are generally geared toward countries who are not on the eligible list, and only process Visitor visa (subclass 600) and the like. Under FAQ for ETA it also states that "If you already hold a current visa for travel to Australia, you will be notified during the application process and you will be given the option of whether to proceed with your application. If you proceed, any ETA granted will not begin until your current visa or ETA expires." It does not distinguish between on-line, or in-person. I saw that another poster from Canada was having this problem and the ETA had stalled. I am also not sure what "expires" means. I have been told that PR visas never expire. Just the eligibility to enter/live-in Australia on them expires. Is this correct?

She is on the list of eligible countries for an eVisitor visa, but the DIBP website states that "Important: If you apply for an eVisitor whilst holding another visa, your current visa may no longer be valid should you be granted an eVisitor. If you hold a valid visa we recommended [sic] that you contact the department before lodging an eVisitor application.". This kind of implies that the current visa may remain valid IF you contact the department. The department here in Dubai is evasive and farms most work out to VFS, so it could take me a while to pin them down. In the mean time any advice from an expert is highly appreciated.