It sounds like your settings should not result in any aging at all.
Changing to "active household only" will cause whatever household you're currently playing to age, which doesn't sound like what you want.
There was a change in lifespan around the time High School came out last summer. That changed where some sims were in their lifespan. There was also a bug that caused other havoc with aging, which has since been fixed.
Are you by any chance talking about sims created last summer or before? They would have been affected by that stuff, but won't be affected any further.
If you're talking about newer sims, I would try removing mods (if any), deleting your local thumbcache file, repairing the game, and trying again. If you still have the same problem then please consider reporting this as a bug on Answers HQ.