With great weather, I still go on the balcony with my Powerbook from end 2004 that I got in 2005. And write, it's so snappy still. Just because it's Tiger or whatever came after. The only thing that's an issue is the battery. Obviously.
The Mac Pro from 2006 works great, minus the video card. I think it melted one day. I now 'back to my mac' or 'ssh' into the box - It has 6tb of media and databases and websites on it that I work on. it's so nice and snappy, probably because of those dual core cpu's.
The iMac from 2009 is slow now, because i force el capitan on it and while it helps, it has lag spikes and it makes premiere pro unusable at this point. I can't wait to upgrade. It had some issues, the PSU got replaced, and a few little things on the motherboard. I can't wait to get the new iMac and then put SSD in the old one to give it another year of speedy-feelings usage.
The monitors are hard to say they are fine. It's a high resolution, but the retina on iPad etc spoil you.. the powerbook now look more washed, even though it's actually fine. The iMac however is 24" and the backlight is giving yellow areas on the screen. Another reason I want a new one.
The durability of these devices are just fine. I never felt like oh wow, it's been 6 months, lets do a fresh windows install on my new pc, .. That hasn't happened ever, I just backup, upgrade, and continue using it.