No such thing. There are lots of variables to what makes an audio interface "stable or reliable". In theory if you follow the manufacturer's test systems or requirements most any interface should be stable. However that's when the variables come into play since most people's systems are not identical to those specs quoted in the blue or red paper (ideal specs). This is why Windows PCs get a bad rap, because there are less variables in Apple Mac hardware configurations. Now, writing great drivers is a whole other issue, and lots of companies are better than others. However, even great drivers on the wrong system can make an interface seem less than reliable. Add in the possible twirks and pitching of your average DAW and it's own requirements and you could see how easily things could go sideways.
Driver wise, Metric Halo, RME, MOTU and plenty other companies put out great code that when paired with the proper setup can go years without a hiccup. However just like any other company they are not without their issues (see: RME Fireface I/O jack corrosion issues, or MOTU digital output error issue, etc). No company is immune to reliability or stability issues because there are just too many variables. As far as hardware reliability in general, you get what you pay for. The best constructed audio interface that I've come across so far is the Prism Orpheus, it's built like a tank. Does that speak for drivers, all the possible systems one could use, manufacturing issues or customer support? No. All of which are parts of the "reliability prerequisites". Hell, the Apogee Ensemble is a great device but has been met with "end-deal" driver woes and hiccups on one end and faultless operation on the other end by users. Same thing with the devices from MOTU, Metric Halo, RME, Digidesign, and so forth.
Since you're talking about hardware failure though, that's a different story, slightly. And unfortunately no company is immune. You do get what you pay for, as a lot of time you're paying for better soldering and construction, better building materials, and better QC from in house inspectors as opposed to mass machine built equipment botched together by 3rd party overseas contractors that make bread toasters in the same plant as your interface. Still, even the best of these companies are going to have problems every so often. Surely a car has better QC than most interfaces, but they even have to be recalled sometimes. Obviously certain countries are known for having the proper industries and plants to do better jobs in house.
Focusrite is actually a very reputable company that puts out very respectable and relevant products. I can't speak about the Saffire unit (it is a budget unit though), but I've generally had no problems with some of their other products (Liquid and ISA range). I'd say unless you're just not too into the sound of the unit and/or just want a better interface for audio quality improvements, then just stick with it or add another device along side it.
Knowing the difference between a "prosumer" interface and a professional interface can get you a long way toward reliability though. I'll leave that to you to draw the line between the two. That said, what are you looking to spend on a new interface? If you aren't willing to pay for the perks of a pro device (which includes longer warranty, better support, better PR, better QC, etc)....then you're better off just keeping the Saffire honestly. What's your budget?
Last edited by The Machinist on Sun Sep 21, 2008 7:01 pm, edited 1 time in total.