General thoughts:
The Desksense plugin performs well and produces a response with no lag each time I try. I'll be honest here, I have not stress-tested yet. The software is easy to use and is very intuitive, though the built-in functionality to automatically stitch together very long prompts would be a welcome addition to its capabilities. You can do this with ChatGPT with careful wording - Google it or ask Desksense!

On their website, they say the following:
Desksense has a word limitation of 750 words per query. The limit of words in your plan is the total number of responses you're getting from Desksense. You'll see a word counter after each response.
One Query ~ 3500 characters ~ 750 English words (Max)
Count of words may vary for other languages
Regenerate will be counted as new query
Access to additional increase in word limit includes Free plan

When I asked desksence the following question, the following were the respective replies:
Q1) How many does desksense's prompt allow?
A1) Desksense's prompt allows up to 2048 tokens.
Q2) How many does chat GPT-3.5's prompt allow?
Q2) ChatGPT-3.5's prompt can have a maximum of 4096 tokens, which includes both the input message and the model's response. Tokens are chunks of text...

I get that tokens don't represent characters but chunks of text etc., but I would expect that given Desksense is Chat GPT-3 based, the answers to the character limit be similar.

I had an issue with their support, but I'll let you make up your mind if it was a misunderstanding or not:
I reported a problem where I could not delete my prompts and the reply I got from Desksense support led me to think that they didn't read my question. I complained about this and received a placatory answer, but they didn't really solve my issue. I was told that it was a known problem and that it would be fixed in the next release. And about 2 days later there was a new release (That included the emoticons) and the prompts auto-magically went away. I wonder if the new release was not scheduled if my problem would have been solved so quickly.

Closing thoughts:
This software is probably the culmination of sleepless nights, blood sweat and tears on the part of its creators and they deserve credit for that. I generally like the look and feel and their execution of the concept, but I'm not sure if I actually need it just now.

Though I had some reservations, I'm sure the software and service can only improve. I think that they deserve a chance and you should try it out for yourself. Another plus side is that you will be grandfathered into the one-off flat rate and will not have to pay monthly for a subscription.