You're right that the cost will accumulate.

I'm not a professional domainer, but "a guy with lots of ideas and no time". Every once in a while I thought of some cool idea, struck a name and bought the .com "just in case I have time to develop it".

I initially used Google Sheet to keep track, but it doesn't remind me of renewals, and some info I want to be dynamically updated.

Oh, another thing I use Every.ID for: keeping track of software purchases, esp. LTDs (Life Time Deals --- SaaS but you only pay once). It's literally a category in the app.