Does anyone know where I can find a mod that makes sims refill their need bars more often (i.e. when bars are halfway through instead of red).

That, or a mod that pushes refilling needs over other activities.

Nothing?

You can try with an xml override mod for the "Motives" _XML resource changing the Intensity settings
for the primary needs. I think that determines (or at least concurs to determine) the urge (DesireCurve)
to do motive filling interactions, but that part of the game is pretty complex and I don't have much insight about it.

If you have such problems (Sims wait too long to refill needs) maybe it's also because the game lags
and the engine can't keep up, so this solution may tax the system even more.

Thanks, I might take a look into it once I get some free time.

As for the lag, it's strange, but the game runs smoothly, the sims just don't take care of themselves until the bars are in the red. It's a bit frustrating to see the bars 3/4ths empty, but the sim choosing to watch television instead!

I personally don't want any disable-autonomous-x mods in the game, so I would prefer to see something about refilling motives be bumped up in attractiveness.