After experiencing a strap sliding off my first electric guitar, about 30 years ago, almost hitting the floor (thankfully I grabbed it, but a terrifying experience for a young guitar player), I realized that this was not a situation I wanted to repeat.
I did my research, and ended up getting a set of Schaller strap locks.
Since this, I have owned more than 20 guitars, and I use S-locks for all of them. I have never had an accident using these (just make sure that everything is tightened from time to time).
The nice thing, is that you only need the full set for the straps you use on a general basis, and then buy the screws separately if you have more guitars than straps. This way you can have security that your precious instrument is safe but at the same time a more economic solution than needing a complete set for each guitar you own.
The design has changed slightly during all these years, but the product available today is even more dependable than when I started out, so I cannot else than highly recommend these. And if you end up selling the guitar, you can restore it to stock specification and keep the screws for your next axe.