Pre/Power having Better Performance Over AVR? Mostly yes if you are comparing both with identical capabilities.
Pre/Power setup having a Better Shelf life over AVRs? Unlikely. Electronics tend to fail over the period of time. If there's a cause concern in the usage which could damage the electronics ; that would affect the Pre/Power setup as well, why only AVR?
My last AVR Marantz SR 7010 lasted 4+yrs (its Still Working Absolutely Perfect with the New Owner) , Only to be Replaced due to Upgrade to SR 8015. The Previous AVRs from Denon and Yamaha worked fine for 2+ years before I upgraded. Again they were replaced due to upgrade and not because of any issues whatsoever. I did have issues with Denon Models earlier but most of it was rectified easily. I usually stick to Flagship models and credentials like heavier weight, no overheating issues reported, Made in Japan, Gold Caps or Cu plated body etc impress me a lot. I usually don't tinker with AVR a lot, once Audessey is Run, I don't meddle with the EQ settings unless I'm forced to. I usually buy AVR from Grey Market (without official warranty) because official warranty in India is mostly poorly managed/honoured to say the least.
My 2Paisa: If reliability is the main concern, Look for a AVR Manfacturer who gives at least a 3yr warranty on their products, if you don't mind spending a bit more ; look for Models (Pre/Power or AVRs) from Well known (for Reliability) Manfactures like McIntosh, Luxman.