Well, they all vary, I suppose, but the continuous symptoms thing did not seem to be an issue with my insurers.
Claims take at least a few weeks to process, so by the time anyone is having to actively consider whether to pay out, I would imagine you’ll have passed the six-month milestone anyway. And if not, at least your claim will already be in the system, ready for when you do reach the six-month mark. Better to put it in sooner, IMO, than put it off, and face: “Why didn’t you claim as soon as you knew?”, or even: “You have missed the time limit for claims!”
As for the proving - many MS symptoms are almost impossible to prove anyway. If you went to the doctor the day after the six months, would she be able to PROVE you’ve still got minor numbness? I can pass the “pinprick” test, even though it does not feel, to me, as I know it should - i.e. it is so subtle that I can tell the difference between sharp and blunt, yet “sharp” does not feel so sharp to me as I know it once did - i.e. it feels a bit like somebody doing it through a towel, or as if there were a plaster on the skin, dulling the sensation slightly.
My physio notes did say I had a weak ankle and a couple of other things, but they were so minor I was not even aware of them until he said, so I guess that must have satisfied as my “persistent symptoms”. It doesn’t need to be very serious, and you certainly don’t have to be incapacitated.
I know it runs contrary to what a lot of people believe about insurance Cos, but in practice, they seem well aware that a high degree of recovery is likely, from early attacks of RRMS, and don’t use your recovery against you in the claim - they know it’s still a lifelong disease, no matter how much better you seem in the short term.
My policy was through work, and like you, I was worried recovering well would be a sticking point with my claim, but not only did they settle anyway, but I was told unofficially by HR that the company had had several prior MS claims, and it was not usually a problem, because they did recognize good early recovery is a common, albeit not universal feature of the disease, so would not usually oppose a claim on that basis. I know that has not proved true for everyone, and some here have faced problems about it. But I can only say what my experience has been, which was that they accepted it as a “normal” aspect of the disease, and not a reason not to pay.
I honestly can’t predict what the line would be on non-disclosure of shingles. Yes, it IS a nerve thing, and there’s some evidence it may be linked to an increased risk of MS. But if it was years ago, and had resolved completely, with no sign of complications, there’s not really any reason you should have thought of it as something you ought to declare. As you say, you can’t list everything you’ve ever been to the doctor’s about - particularly if there were no lasting consequences that you’re aware of.
I’m afraid you’ll just have to keep your fingers crossed they don’t seize on that as something that would have increased your premiums, or caused you to be refused cover. No way of knowing 'til you try.