Stayless masts are generally MORE reliable
The mechanics of constructing a rig that will stand up to the forces on it are well understood by naval architects. This is true for stayless spars as well as stayed rigs. There is no problem designing a stayless spar: it is just a matter of calculating the right sections and scantlings from the forces involved, with appropriate safety margins. But for reliability, stayless spars have considerable advantage over traditional rigs. Masts on production boats don't come down because they are poorly designed, and rarely because they are poorly constructed. Instead, they fail because of delayed maintenance. Ten years or corrosion (or a manufacturing defect) causes a tang or swage or wire rope or bolt to fail at the worst time, and down she comes. BUT: a stayless spar does not rely on tangs or swages or bolts or any of a hundred other pieces. And an aluminum or carbon fiber tube needs no maintenance. These spars will outlast the boats they drive. Short of running it full speed into a bridge, you'll have a hard time hurting it.Of course, stayed rigs are faster. Everything is a compromise. Especially boats.