Ime, there's not much u can actually do to guarantee an IT to remain stable. A true mystery, IT are notorious for going unstable or stable when ever they want over a period of weeks, months or years.
Also, they can look complete opposite in another persons tank.
It's not often you end up with a fully stable 24/7 tiger in your tank. More often you may have 1 or 2 an the others are semi. I'm lucky, most of mine are stable. What helps them Display more ime:
Subdued lighting
Semi aggressive tank mates
Decent wq and strong filtration