Aging off or on and why?

Aging always off. I like to play with the same set of characters for a very long time. I sometimes say I'm going to age them up manually, but so far, I never actually have. I have never played a second generation ever in this game. Lol. I do play multiple households in a save and have over twenty different game files though. I'm always coming up with new ideas.

Ageing off. I don't want to dress up my townies every time a toddler or a child grows up with some hideous outfits. The households I play with have a custom lifespan I manage manually. 12 days equals one sim year, 1 full year with 3-week seasons equals 7 sim years. Every 12 days I change my sims outfits, every year throw them a birthday party. I keep babies for 12 days, toddlers for 72 days, children and teens for 1 year, young adults 2 years, adults 3 years, elders 2 years. My sims live 10 sim years which is 840 sim days and around 70 years. That's terrifyingly a lot but that's the way I like it :)

On. I'd get bored to tears with everything stuck static like it was in TS1.

Aging off.

I play with far too many different households to allow everyone to age up on their own. Not to mention, I play very slowly, so I wouldn’t be able to keep up with everyone.

I'm a rotational player with one full rotation (36 families) being one full year. I play 3 families per month, so I know when each sim's birthday is. I keep aging off and then use birthday cakes to age sims up from one stage to the next when appropriate. Then I turn aging on for one full day for the townies so that they age up appropriately, too.

Off for townies and on my for my household. I started out with it on for everyone. Then one day I realized my neighborhoods were all empty because everyone had died and the game wasn't filling houses. I put a bunch of gallery sims in the houses at first, but eventually I decided to start fresh and turn aging off. I played Sims 2 a lot more than 3, so it doesn't bother me to have the townies stay the same.

As a TS3 player I always preferred Epic lifespans. I just started playing TS4 recently and was surprised at how quickly Townies were aging up so I went and turned aging off, or so I thought.
My Sim had made friends with Summer Holiday and got an invite to her birthday party which she went to and sure enough she aged up near the end of the party.
I have MCCC installed which I discovered recently and in future will probably increase the lifespans to something more like TS3's Epic using that.

But after reloading a save from earlier that day, again Summer sent a birthday invite at the same time of the day. Using MCCC I checked and she was at day 85 of 96 as a young adult, so what is going on here? Does the game randomly generate birthday events for non-played Sims? (Although it doesn't seem like something random as it was the same Sim, unless the selection is done at the start of the day perhaps?)

Just to clarify, I have Auto Age (Played Sims) set to No and Auto Age (Unplayed SIms) unchecked.
I had been playing this game for a time with them on, so I don't know if I may need to start a new game to avoid this.

Off.
Each of my Sims has too much to do and achieve, things to unlock, traits to buy in order to build the character ever since they are toddlers.
I just put too much time and effort in every single one of them to let them go :)

I think I've never had aging on in any Sims game ever. lol When I do something, I want it to last forever, which applies to almost all things in my life. I still have some clothing I bought at 14, and I'm in my late twenties now. Same goes for sims. Some of their kids are the same age or even older than them, but I never cared for realism anyway. lol

I am a generation player so aging on and letting go if my Sims is important. But as I am also a rotational player and as someone who HAS to have some control, I only have aging on in the household I am playing in at each time and have aging off for everything else.

I also play on longest lifespan (that the game allows without mods) and with 28 day seasons. I do plan on aging some Sims manually especially in households I don't play as much in and are mostly support Sims or secondary characters but I usually just let my Sims age up and yes, die when their time comes. I have even killed some intentionally.

Now, that being said, it doesn't mean that I won't feel anything when my favorite Sims die but it has to happen. It happened with both Sims 2 and 3. But I always reserve the right of keeping them on as ghosts and usually invite them into the household (usually via the cheats because I am way too impatient). Not all of them of course.