I'm with Kurblius, great advisor bonus is one of the best ways to get a stability boost. Invest as many magistrates as possible into "paint portrait" to keep your cultural tradition between 85% and 95%, then every advisor you buy will be 5 or 6 stars. I find that I get the great advisor random event most frequently when I have the advisor that gives a legitimacy boost (can't remember what they're called) but hiring a 5-star artist is probably the best idea, because even without the +2 stability from great advisor, you get +15 monthly investment in stability.