This is honestly the best vehicle I have ever owned. I've changed the engine oil and filter every 8000km (every 2-3 months). I changed the spark plugs and transmission oil at 220,000km. I've drained and refilled the radiator 3 times. That's it for major work. I've changed the front struts and rear shocks once. I'm on my third pair of brake pads. It still has the original freaking battery! The only real issue I've had is pulsating front brakes. I'm on my third set of front rotors. The second time I changed the pads and rotors and a brake pulsation in came back quickly, within 30,000km. I just recently replaced the front rotors, pads, and calipers to hopefully eliminate the pulsating for good. That's it. The engine is still strong giving good fuel economy (8.5-10.0L/100km depending on life) and still consumes very little oil between oil changes. The clutch and transmission are strong. Drives straight down the road.
I've been thinking of getting rid of it because I don't know what my break at any time, but now that I've passed 400,000 (I'm now at 401,800 today), I kinda want to see how far it will go. It really is our daily driver. I was thinking about trading it off next summer, but I won't get much for it. So I was thinking of just keeping it as an extra vehicle. But it's running so good I don't REALLY need to get rid of it. I dunno. I am a firm believer that if you use a machine regularly and keep up on the maintenance, it will last longer that if it spends quite a bit of time sitting and not moving, hence the term "Lot Rot". A used car sitting on a lot for a long time deteriorates, rusts, seizes up, etc... and becomes unreliable quicker.
I would not shy away from purchasing a used Mazda 5 with high km's. The engine in this vehicle is a strong one. I can't speak on the automatic transmission as mine is a manual, but I can say the manual is also dead-reliable; same with the clutch.
Overall, very happy with this vehicle. Best vehicle I have ever owned.