My g/f has a 2016 Mazda CX5 and I am in the process of determining if it's worth keeping. It has around 100k miles, and generally has had an easy life.
If you don't have any likely high-$ candidate maintenance items needing doing soon, I'd certainly keep it.
Over the past 40 years, I've had several vehicles. Including three Mazdas. They've each been durable and well-made, with a minimum of issues. Even more reliable than a couple of Hondas I've had.
Had a 1996 Miata that I truly flogged in the winding mountain roads in my region. After 150Kmi it still looked nearly new, and ran exceptionally well. Of course, my maintenance style is fairly aggressive, which keeps ahead of the maintenance curve. (Can't easily cope with getting stuck in the boonies, along some of the routes I took with that Miata, as it would have meant many 30-50mi hikes back to "civilization.") About as error-free as a car can get, actually.
While I haven't had my 2016.5 CX-5 for very long (third year), it's going well. Nothing's failed outright, except the serpentine accessory belt (which was overdue). Typical maintenance items have come along at the expected times. (Brakes, belts, fluids, filters, battery, etc.) With north of 110Kmi on mine, now, it's nearing time to take a harder look at the engine bay's hoses and "rubber" bits, and I'm watching the suspension components closely. Just a matter of time before the hoses bushings begin to show degradation. Cooling system is in good shape. Brake lines, calipers, seals have remained good. The transmission is still fine. I fully expect the car to last a good long while (another couple of decades), particularly as these days I'm much more sedate and easy-going with vehicles.
... there's a vibration that needs looking into. I'm generally handy with cars and the question is basically when can one expect items like alternator, water pump, etc to start doing off?
IMO, the CX-5 is one of the great cars, in terms of reliability and low general maintenance costs. But mechanicals and "rubber" bits do age and need to eventually be replaced. I'd say that the printed schedule (from the manual) is a fairly good estimate for inspection and replacement of things. Was on the Miata, the Model 3, and appears to be so with the CX-5.
The one surprise I got was when the serpentine (accessory) belt went south, and the belt and tensioner needed replacement; hadn't been replaced in a timely manner. Next time around (in another 50Kmi+), I'll likely also get the water pump done. I don't imagine that the alternator's likely to go anytime soon, but it's easily enough replaced.
As for that little vibration you're having, have you determined under what conditions it occurs? While idling the car in neutral? While applying the brakes? While driving at certain speeds? Likely to simply be an out-of-round or flat-spotted tire, tire balance, or a warped brake rotor. Could be loose suspension or steering components, but those ought to be easily identifiable by any shop. But without knowing more about when it happens, ...
Big-ticket items can include suspension + bushings, transmission, and of course the actual engine itself. But most of the other bits and pieces tend to be durable and generally occur where you'd expect them in any maintenance regimen.
If that car you speak of has led a mostly "easy" life, and it's treated well, IMO there's little reason to not expect it to last for many years to come without high maintenance costs. Just keep up with the basic, to-be-expected standard maintenance most any vehicle requires, and you're likely to experience a minimum of costs out of the blue. Mazdas generally are pretty decent, that way.
If looking to keep some costs down, assuming you've got the time and basic tools to do the jobs, one can easily DIY the spark plugs, filters, brakes, suspension arms, shocks, suspension bushings, along with all the fluids of course. Hoses can be a bit of a pain here and there, but most are simple enough. The water pump, radiator and alternator can be a bit of a pain, but still are DIY grade items if you're willing. A good independent shop might save you quite a bit on costs as compared to a Mazda dealership, depending on where you area, if wanting a shop to handle some of the "bigger" items for you.
In short: IMO, the CX-5 is a very good car and, if well-treated and maintained, it is likely to last decades at a cost (of maintenance and ownership) far lower than many other cars.
That's so hot 
