OK, you're not going to stop the TRIAC failing 100%, but you can increase it's odds - first use a MUCH higher rated TRIAC (say 25A or 50A instead of 10A), secondly you can buy special fuses for TRIAC's, which 'some of the time' will fail before the TRIAC goes S/C - but these cost more than the TRIAC's, so it's not a cheap option.
I've repaired many disco light units over the years, and basically when a bulb goes it takes a TRIAC out, most of the time! - it's not cost effective for a manufacturer to over rate the TRIAC's enough, or to use the special fuses.