I'll echo my comments on your parallel inquiry:
Internal carrier leaks are not common on the ARB, known or unkown. They rarely leak internally and generally the cases we've seen with internal leaks are either really old ARB's (we have customers with 30+ year old ARB's, hell mine are 18 years old) or get some debris working through the fluid such as broken gear bits, bearings that have come apart, moisture, etc. I for example have never warrantied a locker because of internal leaks, it's always been on 5+ year old lockers and rare at that. For example we've sold hundreds of Air Lockers in the last few years along, we've sold ~20 bonded seal (the internal ARB piston ring) in the last 10 years and many of those were lockers that didn't come from us.
The more common leak is either the seal housing o-rings (now actually quad rings) or the bulk-head fitting. The seal housing is a troubling leak as you have to open the axle back up to repair. That said with a clean install (and the newer bulkhead fitting kits) leaks are rare overall. We've shipped 100+ complete 3rd members w/ARB's in the last few years, zero come-backs. I've replaced seals in my personal ARB's once in the last 18 years. I'll do them again next time I'm in the axle for service. Poor installs (dirty, unseated seal housing, fluid contamination, etc), the seals can fail much quicker.
The ARB rarely fails to engage with leaks, the compressor can generally outwork the leak BUT it's either running frequently (as opposed to a few seconds when you engage) or constantly. Either way it doesn't leave you stranded as it either works or its open-diffed. Clear as mud?
