How long between referenda?

We in the UK don't have much of a tradition of referendums, and we don't have a written constitution, so to the question of "should the Scots have another independence referendum?" or "should we re-run Brexit?", our politicians simply shrug and carry on as usual.

But is that really good enough? Both of those examples proved to be marginal decisions and circumstances change. But equally you can't just change your mind as a nation every few years; that would make long-term policy making impossible.

In the absence of a written constitution, our Great British Tradition of Keep Buggering On comes into play: kick the ball into the long grass (for the uninitiated, this is something Donald Trump does to his opponents at golf): too difficult, file it under Virtually Impossible and focus on more urgent matters. But perhaps the biggest problem in British politics is short term thinking.

If my main complaint about the above two referendums is the narrow victory margin, it seems logical that I can't justify a re-run if the margins remain narrow, even if in the other direction.

The biggest problems with both issues is that they were driven by fanatical ideology; maybe we shouldn't allow fanaticism to define our future.

My solution to this problem is:

• set a future date for a repeat of each referendum, perhaps 25 years hence (how's that for long grass?)
• subject to certain criteria being met, those criteria being measures of support in the relevant electorate for the poll; for instance in Scotland a 75% majority in the Scottish parliament for a party whose manifesto for the election for that parliament specifically included an independence commitment. Similarly, if parties with a specific manifesto commitment to rejoin the European Union were to, between them, get 75% of the seats (or perhaps 75% of the votes) in a UK General Election
• Once a referendum has been thus initiated and completed, whatever the outcome, the clock would be reset for a further 25 years
• These rules to be set in stone in a law, with a provision that the law would require a 75% majority vote in both Houses of Parliament to overturn it

What do you think, dear readers? Would you like a constitutional convention to consider these proposals? To plan effectively for the long-term future? Or would you prefer us to Keep Buggering On?