I've been involved in companies that went 14 years without a disaster. Another company I was involved with had 2 in a span of 2 months, each taking between 2 and 3 days to recover from.
Regardless of whether I need it or not, I sleep better at night knowing a decent plan is in place. Which means I can perform better during the day.
I would need a hell of a lot more than a time savings of 1-2 days to add a whole new database technology to my production environment. Even if I know the tech the installation, configuration, automated backups, and automated validation of backups will likely consume more than 1-2 days to get setup. Then add on the learning curve aspect if I've never used it in a real production environment. Then add on the learning curve for any team members who might not be familiar with it.
Weeks, maybe. A day or two: not worth it.
I think if your architecture is likely to collapse when you shop around for databases, then you built the whole thing wrong to begin with.
For a single, one-off utility, sure. For anything that you ever planned for production, that would be crazy.
Just to be clear, the mentality that onion proposes (at least from my interpretation, though I apologize if I'm misunderstanding), usually justified under a gross misinterpretation of the "premature optimization" warning, is exactly how disaster implementations that end up failing or requiring enormous amounts of engineering time to try to triage and bandage into something usable.