The issue that caused me to notice I had a problem was the amber warning while on holiday, I was in traffic in newquay and put the GAP IID on live data. I had just done around 200 miles pulling a twin axle caravan and was surprised to see DPF issues (assuming it would have passively cleared on the drive down).
Now i’ve thought about it, newquay has a lot of hills and I noticed the DPF was loading very quickly when coasting down hill in traffic, at the time I assumed it was due to the engine not being able to get hot, but I think that with the valve leaking and the engine on tickover, it makes sense that it would have overloaded the breather system quickly.

If your TDV6 is doing them every 170 miles, that could go some of the way to explain some of the crank and bottom end issues people have . The oil must very quickly get overloaded with contaminants and really highlights the need for very frequent oil changes.

Good news about the drain back cap. Even when properly aligned the rubber goes hard with age and doesn’t seal properly hence why I permanently sealed mine. My DPF regen interval varies between 80 and 150 miles. Steady m-way cruise at 65-70 seems to result in 80mile intervals but if I’m on the M1 with its long 50mph sections I get 150miles. The main thing is if you are not getting amber or red warnings there is nothing to worry about and it will take care of itself. The engine has nearly 180k miles now and I’m thinking of getting the DPF cleaned to remove the ash load. 2012 TDV8 Vogue (L322)

80-150 mile regents does seem a lot (of regens happening), but if it’s doing its thing and not causing a problem (like mine was)…. Mines only done 74,000 miles, so I hope this issue has not shortened the DPFs life .
My daily is a BMW 740d, it can run for hundreds of miles without a regen .

I’m on a steep learning curve on the L322 quirks, I am just hoping I can now sort the suspension height sensor issue and go test drive it to see if the DPF issue is fixed .
It’s showing 2.6V output on GAP IID, but GAP seems to have 2 voltage outputs on each sensor and one of them is showing 0 volts .

Got to love the reliability of JLR stuff !

The height sensors have outputs for the suspension height and the CVD system.If the car is stationary the output to the CVD sysem likley should be 0v. To be fair the relaibility of these later cars is pretty good concidering their complexity. 2012 TDV8 Vogue (L322)

I was wondering if it's worth having the DPF cut out, cleaned and replaced with clamps so that it is removable in future, but how much difference would it make? I seem to remember someone on a forum doing a DIY clean and it didn't make much difference.
I can live with 170 ish miles but maybe a clean would extend it's life and increase the miles between regens?