@Cotcha
Maybe if people aren't getting results with mindfulness alone it could be helpful to see a psychologist who specializes in MBCT and try the clinical form of it rather than just random apps or things on the internet?
This is a great idea, I think that any form of cognitive therapy that addresses unhelpful thought/action/behavior patterns is going to make a difference but having some appointments where you discuss this in detail would be great. I think the issue for many people that are truly lost in thought is that a lot of time goes by before they remember they're supposed to be mindful. If your mindfulness only lasts for 3 minutes and then you spend 57 minutes being unmindful before you remember, that's no bueno. I think that having more memories (in real life, not just on the internet) concerned with mindfulness will help with people with remembering that they're supposed to be mindful and catching themselves when they are ruminating. You can drill it into your head reading a book about meditation and then consciously trying to remember to stay mindful but some more real life events might help. A meditation retreat would also be a great ideal, although unfortunately not an option for many.
The studies supposedly claim results in 6-8 weeks after regular practice but is this true or does it take longer?
The other thing is I wonder if using mindfulness to cure this problem goes against mindfulness itself?! Am I overthinking this?
For many trials for different therapy type things they seem to like like using 8 weeks of the test vs. placebo, then follow ups later on. From the studies that I recall improvements were seen at 8 weeks after around 30 minutes total daily practice (some studies using methods that may not be equivalent to 30 minutes independent practice, group sessions for example, led by a PhD or MD) but as I recall there were more improvements as you went further down the follow ups. So at the end of the 8 weeks concentrated practice is not when the benefits are fully realized but you should expect some results then, although obviously LTC sufferers are a unique population.
Here is a trial for mindfulness being used in chronic insomnia that used once weekly 2.5 hour sessions with a 6 hour mindfulness retreat at 8 weeks in addition to 30 minutes daily meditation
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4153063/ You can look at this figure and see that benefits are gained long after the 8 weeks for Mindfulness Based Therapy for Insomnia (MBTI)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4153063/figure/F3/
You can see in this figure that there is something going on after 3 months for MBTI, but of course MBTI is still doing vastly better than the control (SM) at 6 months
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4153063/figure/F2/
I don't know quite what that is. It could be that the insomniacs were really starting to pay their sleep debt around 3 months. It could also be they felt well enough after paying their sleep debt that they didn't try as hard to sleep, as opposed to they were still trying to sleep but had decreased physiological sleep drive.
The other explanations could be more biological, a consequence of synaptic reorganization, a sort of "darkest before the dawn" scenario, the brain smoothing out. The idea being that synapses that didn't get used very much would have become sensitized and then when finally used they were a bit too sensitive and would take some time to return to average sensitivity. I would've liked longer follow ups, 1 year, 2 years etc. because I assume that things would have continued to improve beyond 6 months, bar having really paid the sleep debt and decreased their sleep pressure.
I imagine that mindfulness for an LTC will function in a similar way but the benefits are going to be a little bit more drawn out, but the benefits could also be much more powerful in the years down the road. But a journey of a thousand miles begins with one step.
As for mindfulness causing unmindfulness, it really means that mindfulness is exactly what you need IF you can learn to do it correctly

I think taking an approach that's not just learning mindfulness independently would be a fantastic choice for trying to push through that issue. Depending on the person I'm sure some people are going to have less benefits within the first 8 weeks and more benefits down the road once they start to think less during mindfulness, and also learn when to apply it lightly throughout the day, even when doing tasks (Most helpful for ADHD, which mindfulness has proven effective for as well).