Ranking HVAC unit brands based on my own experience

 Getting older stinks! And we all can admit that some folks age better than others. I mean, have you seen William Shatner? The man is in his late 80's and looks like he's in his 50's!

The "aged well idea" can be said for other things too. I have completed 2500+ inspections to date in West Texas, and I've therefore seen at least that many HVAC units. Remember, I have based this info on my own experience only, and your mileage may vary.
Based on this experience, here are the brands that seem to last longer to me:
Trane - It's hard to stop a Trane, and that seems to be more than an Ad slogan. I have seen dozens of Trane units well over 25 years old. 
Lennox - I haven't seen nearly as many Lennox units that are as ancient as Trane units, but I can tell you that Lennox units do seem to age well. The unit in the photo was almost 15 years old, but as you can see, looked much newer.
Carrier - I have seen a number of older Carrier units still going strong. My own home has a Carrier unit that's nearing 20 years old, and still plugging along.
Rheem/Ruud - For whatever reason, this brand seems to have been particularly popular in West Texas in the early 2000's. At any rate, I've seen a number still cruising along and nearing 20 years old.
There are a number of other brands I don't see all that often and therefore can't make a good judgement on their longevity.
I'm sorry if your home has a Payne or Goodman unit. From what I've seen, these seem to be cheaper units and I rarely if ever see them older than 10 years.

According to the US Dept of Energy, the national average lifespan for an A/C unit is about 15 years, so if your unit is older than 15 years, look at it like a WIN and plan for replacement soon!

Maintenance can help too. Whether you reside in Lubbock, Midland/Odessa, Snyder/Colorado City or any of our awesome West Texas small towns, one thing is for sure: In the summer it's hot, in the spring and fall the dirt blows, and in the winter, it gets cold! Employing a professional to inspect and service these units at least annually can sometimes improve lifespans and save you $$ in the long run.