I also vote for Namesilo (and it pays off to check the lowest renewal prices for specific domains such as .co), as GoDaddy is a rip off regarding renewals. That's where they make millions.
Also consider letting go of the domains that aren't realistically getting developed or sold. I know I sat on some for a long time but since I let them expire I never thought about them once.
Nowadays I just keep the domains that do have websites on them, plus a few I'm developing at the moment, and a few valuable ones that are worth a few grand. No domains in my portfolio are low-value without a website.
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