Rick - I guess it depends upon whether your needs could survive
       an outage for some hours...

On our 3494, I would say that the accessor fails about once every two
years or so, sometimes a worn-out motor, sometimes an over-flexed
cable.  The last time was a couple of weeks ago: from service call to
repair time was about 8.5 hours, most of that awaiting a part to
arrive and then a free CE to install it.

A full concept of high availability would include stocking spare
parts on site - as it is too often the case that parts for IBM
equipment are available only in another state.

    Richard Sims