I'm not sure if you'd consider an Altmer in her 130's ancient, but the way I handled her was I gave her wonderfully good fire spells [her line of expertise] and she svcks at almost everything else besides Alteration and fighting with longswords and is majorly weak to cold. She gets horrible sick if she stays in Bruma for too long.
Ancients aren't always that uber if you do 'em right; I'd think most would spend most of their time studying their interests and be horridly deficient in everything else so that they have to rely on other party members for backup.
That's usually how I do all my characters, really, and so far it works nicely: give them a line of expertise where they're good to excellent and have them fall at or below average on everything else. My fighters are awesome fighters, but pit them against ranged mages or archers and they need backup or they die. Assassins, as uber as some think they are, rely heavily on striking first, fast, and before they can be seen. Put 'em in a brawl in broad daylight and they fail. That sorta stuff.
My, I really do have a knack for straying off my original subject if I talk too long, don't I?
Anyway, back on topic, if your old character is a human or beast race and not a vampire, they'll also suffer from the drawbacks of simply being old, so they'll really need help against younger, stronger enemies. Elves and vampires and werewolves each have their fallbacks of simply what they are too, despite not having to suffer from frailties of age, and those help balance out a character if kept in mind.
Generally, I think that if anyone with common sense does an old character with those things in mind, they'll be fine. I've seen some people here that have never RPed in their lives before that can do decently with these even, though they're admittedly rare. And like my dear Uglius mentioned: Just because you've got experience doesn't mean you can't still [censored] up. [Just look at me, lol]