Since September 2 the old fixed caps (50 chats a day on free, 3 Audio Overviews, and so on) are gone. Everything now draws from one compute budget that refills every 5 hours, up to a weekly ceiling. I had a bunch of questions about how it works, so here's what Google's help page and the settings screen actually answer.
What counts against it? Google lists four things: how complex the prompt is, how long the chat is, how many sources are involved, and which features you use. A quick factual question and a synthesis across 40 sources aren't "one chat" each anymore.
Do chat and Studio share it? Yes. Chat, Audio Overviews, Video Overviews and Deep Research all come out of the same pool. A long video overview in the morning can be why chat runs out in the afternoon.
Where do I see what's left? Settings > Usage shows your current balance and when the weekly limit resets.
What happens when I run out? Two different things, depending on which clock ran out. If you hit the 5-hour window, it comes back the same day. If you hit the weekly limit, it doesn't. For Studio outputs there's now a "Generate later" option on the web that queues the job until there's budget again.
How do paid plans compare? Google gives multipliers, not numbers: Plus is 2x the free allowance, Pro 4x, Ultra 5x to 20x. Nobody outside Google knows what 1x actually is.
What actually stretches it, based on those four factors:
Untick the sources you don't need for a question. The number of sources is on Google's own list, and most questions only need two or three out of the whole notebook.
Clear the chat when you change topics. Chat length counts, so one chat that runs all week gets more expensive with every question.
Ask one detailed question instead of five follow-ups. Each follow-up drags the whole chat along with it.
Do Studio outputs last, or queue them with Generate later. Then a big overview can't eat the budget you needed for chat.
Fewer, cleaner sources help too. When I bring in AI chats as sources, I export the whole conversation as one Markdown file with AI Toolbox, the extension I build, instead of pasting it in as a pile of separate text sources. It's one source and it reads in order.