Considering the systems have the same fans and heat sinks, any of the expected lifespan would be completely independent of Apple manufacturing, as all the Apple parts are the same.
The processor and SSD are independently made, and the SSDs are essentially the same, so they will be as reliable. Technically, we could argue that larger SSDs will have longer lifespans due to the number of actual die on the drive, allowing for more space to be corrupted before the drive is useless (I don't know too much about hard drives, so don't take my word for that). The i7 processor runs hotter than the i5, so there is the potential that it could go bad more quickly, and potentially damage surrounding components. RAM produces some heat, so the more RAM you have, the more likely your computer will be damaged.
Overall, the there is probably no benefit of having a maxed out system, in terms of lifespan at least. The parts of the baseline systems are sourced from the same manufacturers, and in many ways, they are the same machines externally. If anything, they will produce more heat, and the people using high-end machines are typically pushing the machine to its limits, reducing lifespan.
Matt