(Creator here) I recently moved the website from search.marginalia.nu to marginalia-search.com and gave it a bit of a visual touch up, on the basis that I felt it was working too well to be a weird subdomain outgrowth off my blog.
I do a big recrawl around once every 10 weeks, but I have a RSS crawler that does daily visits and fetches new items. But that should be very low volume traffic.
FYI - https://www.dynadot.com/market/search has a nice way you can filter their Aftermarket domains for sales by Character Count, TLD, No IDN/Number/Hyphens.
I've found over the years plenty of <= 5 character domains that have a meaningful name just from using their search filters.
It's still the same search engine :-)