Kagi search is great, but I'm not willing to pay more than $5/mo for search and 300 searches isn't enough. I have no interest in Kagi AI. Adding more searches would've caused me to sign up again. A rate limit instead of a monthly limit would prevent the "search anxiety" that creeps in as your available searches dwindle. Make it so and you can have my money again.
I also use the $5/month plan, and the few times I have exceeded the 300-search limit, Kagi simply renews my monthly plan early. For me it's just happened a few times towards the end of the month and I was happy with how they handled the situation.
May be Kagi could also consider rolling over unused search for one month. So if you only did 200 searches, the remaining 100 will roll over to next month so you have 400 searches.