I used to shoot Canon DSLR. I had the papparazzi lenses, red rings all round. I never took the thing further than 200 yards from the house. I had the crop sensor so admittedly not armour plated so much like the 5d or 1d.
I moved to Sony A7 a couple years ago and swapped my lens system. Because I liked the idea of increased portability ergo more use.
I have had no issues. I now get to enjoy shooting an a7rii and a pair of Leica Ms. Which I adore using but this is a hobby for me not a profession.
All of these have metal frames. They are all solid enough for normal use. I admit the original A7 wasnt as tough as the a7rii but it was never meant to be.
While my current line up wouldnt take an absolute kicking, i think they are fine on the whole.
When it comes to longevity, I think the question of moving parts comes in. On a DSLR, we have decades of evidence to prove the life of the mirrorbox and shutters. Over time that engineering has been refined.
Mirrorless has the same engineering on the shutter without the mirrorbox to break so fewer moving parts, less to break. All else like
@Apfelkutchen said is the same. Same electronics dependency same battery usage.
Yes DSLRs sip the battery compared to the Sony binge drinkers but that is solved by carrying a spare battery and having to take 20 seconds 2-3times a day of heavy use. It doesnt come as a surprise either. It tells you when you are getting close. So no issues. I laugh when people concern themselves with battery life when it means you take a few seconds to swap it out. Really? You carry a battery pack to get your iphone to last a day yet you moan your camera needs a swap out. Hmm... Ok...
IQ, if you are not printing large and are not a DoF addict, then the smaller sensor mirrorless cameras are coming along leaps and bounds and you will be hard pressed to tell the difference. It is the photographer not the camera afterall right? I have pictures on my wall. Printed A0 size from my brother in law. Some taken on a Hasselblad MF and some on a Fuji x100T. Apart from the Hasselblads being studio and the fuji street, you cant tell them apart.
At the end of the day it comes down to your personal needs. My systems fit me perfectly well. Do I take my cameras into hostile territory frequently enough to need rugged? No so I dont need the full on metal behemoths. Having said that, the mirrorless cameras are far from dainty wee roses that float away in the wind. One thing to note is dual card slots. Mirrorless with this fault tolerance are hard to find and if your livelihood is dependent on those images, then a n+1 dual card option is something to take seriously.
I think and I may be wrong, just my opinion, that unless you are looking for a true workhorse camera that you will beat senseless, then I dont think you need to worry too much either way.
Plus, you can buy 2 Olympus OMDs for the price of one Canon 5d or Nikon d810 so even if they only go half as long, still not a bad choice financially.
Bah! What do I know. Sorry for rambling... Just get one and go shoot! Lets enjoy some pictures and someone please help me learn the difference between snapshots and art! It is ripping my knitting!