I was pretty surprised that Scotland voted against independence last year. As you wrote, it may happen in the future, but I can't see the Scottish leadership organizing a referendum on the issue every two years.
IIRC it was a vote with a good turnout, but a narrow win was scraped by the No vote, and I think a large part of that was down to some intense scaremongering on their part, very little of which was true. A good portion of Scots, quite possibly a majority, would like to remain as part of the UK if
their country starts getting equitable treatment.
I think the Scottish government will propose referendum after referendum until they get the result they want, in the current climate.
In what way does UK treat Scotland badly?
Scotland has suffered historically from poverty and it's economy has always been vulnerable; this has only increased in the 20th century, and it has a fair amount of both poor rural areas, islands, and poor urban areas, all of which can be very expensive to support properly with infrastructure and social care. This support has largely not been forthcoming, especially from Tory governments who have gone out of their way to get rid of the UK's industry, in which Scotland had a considerable hand. Scotland is, for those reasons and others, absolutely impossible for the Tories to crack politically (it's only very recently the SNP has had widespread success, Scotland was a Labour stronghold for a long time) and so they feel they lose little by ruling it with what, at best, is benign neglect.