Is there a way to speed up rendering of grass and trees?

[Twist]

Hello

I have a fairly complex scene we need to render at work for a feature. I can't show you the scene unfortunately but it's a scene with terrain, lots of trees and grass.

1080p render
I have disabled GI to get lower render times (GI didn't add much anyway)
No translucency of leaves and grass.
It's a full frame render

I'm currently looking at 4 hours per frame on a 7950x (max subdivs 10), still with visible noise. I have 500 frames. yikes...

Is there a way to speed up the render up? Even a little bit could help.

Thank you!

EDIT: Forgot to say i've already disabled filter on opacity textures.

[stezza]

I'd stay with Min1 Max 12-18 theshold 0.01 or 0.02
All proxys I take it?

[Twist]

90% of the scene is proxies.

16 samples would take 8 hours per frame I think. I haven't tried it as it won't work in terms of cost (using a farm).

As mentioned 6 samples take around 1 hour and 10 minutes.

I knew it was a long shot since there is no magic button. But maybe there was something I haven't thought of yet. So I'm open for creative solutions to get the render times down