Time for an honest appraisal.

Being having a meaningful conversation about the future of Dreadnaught. At 111000 miles the question of reliability going forward is having to be seriously given thought. As a daily worker there is going to be a time when it all becomes too much and things start failing. There's only one replacement alternative and that is a late gen3 automatic. The question is where is the line, at what point do I duck out? Wait until Dreadnaught is costing money to maintain, when there's no real residual value left but I've had my monies worth? Or get on with it while there are still some tidy low mileage late gen3 automatic Jimny left and Dreadnaught still has a meaningful value? 

And yes this will be a massive emotional wrench as I truly love Dreadnaught but it is a tool to do a job. What to do? 

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

Emotionally there is nothing on a Jimny that cannot be replaced or repaired so therefore it would not be a stretch to keep Dreadnaught on the road indefinitely. However as a business user I have to be confident that any vehicle is ready as needed to do whatever is required. This time last year with the head gasket failed that was not the case and had it not been for the pandemic that inconvenience might have been a week of down time instead of like 9 weeks, which has focused our attention onto robust solutions not just for cars but everything we do. I believe it is called stress testing. What I don't want is to find myself in a situation similar to when I was running the land rover and had to have 4 vehicles to do the job of 3 because of needing the redundancy to cover potential unexpected down time. Dreadnaught is subject to an extensive maintenance programme to maximise reliability but as the mileage increases so do the potential issues. I just don't know if I am round the corner from another major time consuming issue or not?

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.