What is a 3 roll 2 jacket?
That's shorthand for a three button jacket with lapels that roll to the middle button. That's why you can see the (unusable) top buttonhole on the reverse side of the lapel, like the jackets on the suit and stroller wearing men in the illustration.
On a 3 roll 2.5, the buttonhole is hidden by the lapel roll. It's also never buttoned. Primarily an American look, I like it for odd jackets and less formal suits.
On a 3 roll top, the lapel is short as the top button can be closed. This is the classic vested suit.
As we both know, suit styles change. When buying a new suit, how long
should I expect to own it before it goes out of style?
If you are buying classic suits and not fashion items they can last indefinitely with care and reasonable wearing. I wear one or two suits that are more than a decade old every week.
I'll estimate that 400 wearings is a reasonable age for a high quality suit that's dry cleaned infrequently. So, perhaps eight or more years if a suit is worn 40-50 times a year, as it would be in a six to ten suit wardrobe where a suit is worn daily. In a thirty suit wardrobe a suit will probably outlast the wearer, as it also will when it's only worn for special occasions.