I started re-amassing the 1961-65 comics I had as a kid in 1979. Like you I'm a completist. Here's my Want List which of course shows where I stand on some of my favourite through to well into the Bronze Age when I sort of lose interest and lose track:
Flash 106U 107 108 112 113 114 115 120 123 126 127 plus of course the Showcases
But do I really need to "upgrade" my #106?
Green Lantern 4 6 13U 15U 25U 47U plus the Showcase 22 & 23
But do I really need to upgrade these two?
Aquaman - Showcase 33U & 9U 56U
Once again I'm being very picky regarding the upgrades I "need"
Atom - Not even a weak link.
Hawkman - My Brave and the Bold 34 is my "weak link" because it's not quite perfect enough:
Wonder Woman 98-109 111 113-116 124 125 128 138 174U
Justice League of America 3U 5U 6 47U
My "weak" link:
World's Finest -110 113 117
I'm basically solid on my other favourite titles such as Mystery in Space with Adam Strange, Challengers of the Unknown, Tales of the Unexpected with Space Ranger, Brave and the Bold with the team-ups, Sea Devils, Metal Men, House of Secrets with Mark Merlin, Teen Titans, Adventures of the Fly, Adventures of the Jaguar, Captain Atom and Blue Beetle from 1963 onward with some earlier holes. But some such as Star Spangled War Stories, Fox and the Crow, Space Adventures with Captain Atom and Gorgo are tough to find even from 1963 onward! And I have many holes in my Superman and Batman title runs.
But when COVID hit in January 2020 I took "early" retirement at the age of 67 and much of the time these days I can't afford to add to my comic and other collections. But I keep considering looking for a job to enable me to do precisely that!