iOS - realtime AO adds lag, but only after a while

Hi, I'm working with Unity 2018.3.0f2 and I'm deploying on my iPhone XR. My small racing game looks much better with realtime AO activated, I know it's pretty heavy but I thought I'd give it a shot. I was really happy to see that even with that image effect I got 60fps fixed. The thing is, after about 30 seonds the fps slowly starts to drop and it keeps dropping and dropping (slowly, about 5 frames every 30 seconds). Without the AO this issue isn't there. Any idea?

 

Simple: the phone gets too hot (AO is super expensive on phones) and reduces its performance to cool down a bit.

 

That makes sense, I guess I'll have to drop the AO

 

Sadly almost none of the post processing effects are really doable to use on mobile.
A bloom effect with the so called "fast mode" for example, totally kills performance on "older devices" (aka devices from 2015-2016). An empty project on a Huawei P8 lite (Android) with bloom was dropping the FPS to 25 for example.

 

I think color correction or vignetting shouldn't be too heavy, even for mobiles