I see.
mIRC is moving to 64 bits where memory will no longer be an issue so I think it's fine to increase the cache and allow GIF's frame to be cached, I think it's only fair to increase such limit that were made decade ago with different consideration in mind, regardless of this topic.
But I must admit that I would still not be satisfied with a gif showing slowly first and then getting better, I want to display a GIF with normal speed and normal wait from the start.
If you were to animate the GIF natively, it should then be at browser-level speed, so that's ultimately my suggestion.
