How far is too far?

I'm planning on a few long UK weekends away this year, using our Jimny to get there and back.

It's a 2008 auto that's covered 76k, serviced within last year.

We will be using A & B roads as I don't fancy motorways in a 1.3 with only 4 gears.

How far can I drive in one go before taking a break to give the engine a rest?

Until you run out of fuel.  This is why engines took over from horses.

The last few years I have been doing long trips with my 2005 Jimny mostly pulling a 350-450kg trailer and with all I need to sustain myself and tools and parts and firewood and camping gear. Well loaded.
Driving mostly bad gravel roads, mountain passes in Norway up to 1400m and down and back up again. Clutch have been smelly for years
Servicing has been so so but mostly ok.
Most of these trips is over a week or two, approx 2500km thru Denmark, Sweden. I try not to do long hauls but to see the sites and take it slow and easy exploring. Also going to offroad events so not exactly being nice to the car either. Using it for what it was built for.
Some days though I can do longer hauls with 8 to 10 hours of driving. not so many km's as these roads is very hard to get more than 60kmh average speed on but have reached 600km in one day sometimes.

As long as your brakes are good and serviced, tyres good, check the oil, fluid levels and cooling, there is no reason you could not drive all day.
The engine is the least of my worries.
My car has been modified a bit so I worry more for the drive train.
If your car is original there should be no worries.

I have had experience of small mopeds which need a break every hour to some of the most comfortable motorway cruisers which will go for hours (600 miles range). The Jimny is somewhere in between.

I could drive my Gen 3 for 2.5 hours without a break, 3 hours is doable, but after that I am ready for a stop. My Gen 4 is better, may be 3 hours without a break and possibly 4 hours at a pinch. So let’s say 150-250 miles, depending on the roads and conditions. Much further and you need a fuel stop anyway.

I drove 350 miles each way to the BigJimny meet up last year, felt fine when I got out and it was hot. I didn’t really want to go any further in one day.

My Jimny however, would have turned around and gone straight back home.
Robin

Thanks one and all. Seems as if I have underestimated the Jimny big time. 

The only issue you can have on any older car is if the cooling system is inefficient - partially clogged radiator or weak water pump. Hours of motorway driving can eventually cause overheating, especially as an auto dumps extra heat into the radiator.  On really hot summer days, you see far more broken-down cars of a certain age on the hard shoulder.

Jamento wrote:

I'm planning on a few long UK weekends away this year, using our Jimny to get there and back.

It's a 2008 auto that's covered 76k, serviced within last year.

We will be using A & B roads as I don't fancy motorways in a 1.3 with only 4 gears.

How far can I drive in one go before taking a break to give the engine a rest?

I did 3500km over 12 days through Botswana, in my gen 3 Jimny, in December with day time temperatures around 33 degrees celsius. Stops were to admire the view and to fill up with fuel.

No need to worry about the Jimny. Driver fatigue is more of an issue - either stop for a walk around the car once every 2 hours, or swap drivers.