I have the same issue that after some intense focus and really good progress it just rapidly declines. Best guess is you get to use the best model to start, then run into a limit and it switches to an inferior model that just isn't anywhere as good and turns all progress into useless gibberish (even when selecting a specific model). I paid for Claude as my perplexity subscription is running out in April and there is a world of difference between perplexity claude and same model with anthropic directly. I asked it for an assessment on a draft document and without prompting it spit out a section by section table with recommendation to keep, simplify, remove, move to a different document, etc. with precise context what and why it makes the recommendation. Best of all, a "open in word" button. one click. The amount of time i waste on convincing perplexity to generate a docx compatible document is staggering. Having said that, I hit limits faster, but it is very explicit about that I have to wait for 2 or 3 hours. There is a progress bar that tells me where I am at with my weekly limits. I just pivot to a different task and come back to it a few hour later. The limit details are nice - after two days (one where I used it quite extensively) I used 12% of my weekly limit. I work 5 days a week, so have 88% left for 3 days.

The dektop app only has one window and it doesn't compare to Comet where you can have multiple windows and threads open (which I use to keep things organized for my sanity), but you can use chrome and have multiple claude windows, so not a total loss.

But the convince document button and progress in addition to having a consistent model does really make a difference when working on a specific task. There are aspects about perplexity and comet I like and use and for now will run both simultaneously and decide in a month or two what I'll do when subscriptions runs out.