The long s (ſ) and its disappearance from handwriting is a bit of a mystery to me.
Printers had more or less abandoned its use at the beginning of the nineteenth century, although it continued to continued to be used in the Sydney Gazette as late as 1814.
However, by 1816 it was gone, and the typography followed modern usage.
Handwriting was a different matter though.
When my great^n grandfather was born in 1814, the parish clerk recording the event used a long s. Jane Austen also used a long s on occasions in her writing, so we could plausibly argue that when people wrote letters and official documents, they used the long s.
It would be entirely natural to find that people who had learned to write using the long s would continue to do out of habit long after printers had dropped its use, especially if they were frequent correspondents.
So when did the handwritten long s drop out of use?
Short answer is I don’t know. I’d say probably around 1830, and certainly there’s some evidence to support the idea that it was much less commonly used by then.
Fanny Owen, when she wrote to Charles Darwin in 1831 before his departure on the Beagle, appears not to have used it, nor did Florence Nightingale or Madeleine Smith.
Fanny Owen is the most interesting example – Florence Nightingale and Madeleine Smith were born in 1820 and 1835 respectively, which would have meant that by the time they were learning to write, the long s had dropped out of use in printed books, but Fanny Mostyn Owen was born in 1806, which suggests that she would have learned to write in the early 1810’s, at a time when the long s was still in use, but may no longer have been taught in books of penmanship.
And this leads me to an interesting little puzzle – I was looking at a Facebook page from the East Yorkshire archives that included a recipe for mouthwash tentatively dated to some time around 1890

and there, in the second line is the word glass written as glaſs.
Obviously the dating could be wrong and the document could have been written well before 1890, and the person writing it could have learned to write using the long s even though by the time the document was written it was no longer in common usage.
And while I’m prepare to stick to 1830 (±5) for when it dropped out of common usage, there’s evidence that the handwritten long s was still in use in 1842

suggesting that some people were still using the long s in correspondence in the 1840’s, although the author could conceivably have been old enough to have learned to write using the long s.
Likewise in the course of researching this blog post I looked at one of Wilkie Collins’ letters from 1860, and towards the bottom of the letter there is the phrase Miss Halcombe’s Dream which looks to have been written Miſs Halcombe’s Dream

Wilkie Collins was born in 1825, meaning that he would be of an age where one would have expected him to have learned to write without using the long s.
It could of course simply be a slip of the pen, or it could genuinely be a long s. One example does not a usage make.
I think I might have found myself a little problem to worry out …