Time for an honest appraisal.

I'm curious what you consider will need attention soon reliability wise? Many Jimnys achieve much higher mileages and over much longer periods of time. Aside from severe corrosion I can't think of any issues that would not be economical to repair.

I'm at the point with my 2003 Jimny where the rising price of a replacement means I can justify almost any repair necessary, and that has represented a significant change in my attitude to car ownership. I normally run cars into the ground and bin them when they need a significant amount of welding, but right now time spent welding is a cheaper option than replacement.

This is not an easy question, especially now, that the prices of used Jimnys are quite high.

From a cost perspective, I would think that Dreadnaught loses less than a newer automatic Jimny per year. So regarding spending the least amount of money the answer would be: keep her.

If money is not the main concern, my proposal would be to continuously look for a suitable automatic Jimny, and go for it when you find one, because finding a suitable Jimny might take some time.

I hope this helps you at least a little bit.

If you have no desire to replace then it makes sense to wait until it starts costing money or is repeatably heading for a garage.
just being new and low milage is no guarantee of reliability. I swapped a 2012 (4 years old at the time) VW Polo with 25K for an older Jimny with more miles. Why ? The VW cost a fortune in repair bills as it was complex and unreliable. 
Still waiting for the Jimny to miss a beat.
My 2CV (1986) has toured Europe, my 1960 land rover has been to the moon and back, still 100% reliable.
I would wait until rust takes hold or you are running up more than the deprecation on a new vehicle in repair bills. You are very unlikely to equal depreciation which = keep it
Better the devil you know
Of course just my opinion, your needs and experience may differ from mine.
Mike

There is no easy answer to that question. As Scimike says, newness is no guarantee of reliability. It's unusual for a headgasket to go on an M series engine, especially at your mileage. Preventative maintenance and regular checks will help you avoid being caught out. I can't really think of any age related failures that could creep up on you. Crank pulley failure perhaps? Clutch? Transfer box chain? I've had a couple of them fail so I try to keep a replacement transfer box in stock. Obviously you are already familiar with the various bearings and bushes.
Keeping parts in stock is a good way to reduce downtime. There aren't many jobs on a Jimny that can't be DIYd.

I do understand your concerns, but if you want to avoid major issues just keep servicing as you do and fix any minor problems before they develop.
Yes it's true a lower mileage and newer vehicle "should" be more reliable, but the added complexity of modern vehicles has some what undermined that statement in my opinion.
Unfortunately the only way to get yourself in a situation that your vehicle is ready to go 24/7, without any issues, is to factor in redundancy; so you need a standby vehicle.
Anything else is just fingers crossed reliability
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I bought an MOT failure (rusty) Jimny and I'm slowly stripping it as and when I need parts for mine. I know not everyone wants a scrap car hanging about, but it's certainly an economical option and allows me a quick turnaround if something does break.

There is also another option worthy of consideration, refurbish Dreadnought..... Get a price from Terry aka "Jimny Dr" for a full body off refurb, refresh/rebuild the suspension and drivetrain as far as you desire..... 3-4k gets you a shell which has seen all the bad bits made bombproof and will last another 10 years + before needing any work, all Raptor coated....... That with fresh suspension and brakes, it would feel like a new car, mine did....

Have a ponder, changing cars is going to have an element of cost or loss to the farm. If the refurb is below the cost overall of new, you would probably end up with a better car doing your own build.

You could also consider some mods at the same time, a pick up may be useful and not much more cost..... But certainly some Gucci suspension.....

The question of reliability, for a few hundred pounds you could have a complete engine, gearbox and transfer box on the shelf, ready to fit....  They would likely sit there a long time, but if you need that security it won't cost the earth..... 

In terms of cost verses benefit, the refurb should be a strong contender..... It would also be an opportunity to get a little of what you want, put in to the vehicle you drive.

sniper