It's one of the great investments of the past decade, and its value-creating formula can still work from here.When it comes to boring investments, United Rentals (URI 1.05%) likely makes the short list. And yet the stock for this equipment rental company is trading up 35% year to date, as of this writing, crushing the 12.5% comparable return for the S&P 500. Moreover, its returns in 2025 aren't a fluke -- the stock is up 1,310% over the last 10 years, and that's before accounting for its dividend.Boring sto ...