Game systems for the long haul

I started out playing with GMs who ran long-haul epic campaigns that lasted for years, if not decades. 

Now everything new coming out seems to be set up for one shots and conventions.  Nothing seems to scale well as the characters level up and get more powerful.

Any ideas for a system that doesn't break after a couple dozen sessions?

We used the d20 modern system for Fringeworthy as well as Bureau 13 for several years. It was only at the end that it became too easy to break.

For games with a lot of roleplaying over dice rolling i would go with Fudge though, simpler dice system.

Once I had played a couple of the Chaosium D100 RPGs back in the early 1980s, I developed a dislike for leveling up characters.  It didn't matter that much with the Tri Tac RPGs of the 80s and early 90s, since a well placed bullet, or arrow, or knife would ruin your day despite your high level. 

Without all the free time I had as a kid/teenager, I also find shorter campaigns preferable.  A couple years per campaign is just fine.  I get that with levels you just want to keep going until you max out (I do that in RPG videogames quite often). 

All this to say: I don't have any suggestion for an RPG with levels that won't break at the higher levels.