There's no reason to believe that a time requirement is a good protection against random politicians saying outrageous things. In fact it probably makes things worse because it gives obvious timelines for a campaign, so whenever the possibility opens up it pretty much guarantees all the outrageous politicians coming out of the woodwork.
Cool. I like the idea of that. Other things that seem non-reversible...
- building nuclear plants/weapons
- burning fossil fuels
- dismantling the NHS
If half the population is against it, it doesn’t matter if it’s 51% or 49%, it’s unpopular enough that it is tearing your nation in two.
Imagine the US civil war came down to a vote: “Sorry, 50.1% are in favor of slavery so we’re just going to keep practicing it in all of America”. Would the 49.9% be happy to live within that union? How about vice versa? The division is too deep.
Let's imagine for example that genuinely 55% of the population want to remain part of the UK, and so remaining should win given a completely fair and accurate measure of the population's mood. However, every measurement varies for a variety of reasons, for instance what outrageous things some random politician has said in the last few days. If we were to hold a referendum every year, then you'd be bound to hit a year at some point fairly quickly where the random variation pushes the result over the 50% leave threshold. This would trigger the non-reversible transition, and the referenda would stop happening.
There's a reasonably strong argument for this reason that non-reversible decisions should require a greater than 50% majority. That's why amendments to the US constitution require a 2/3 majority vote to pass.