I used to use binders, but took too much space and I never really looked at them.
1970-present I use penny sleeves on every card and them put them into white set boxes. I then label the end of each box so I can see what it is without opening it. Lot less room, but putting them into penny sleeves first can take time.
Pre 1970 all go into penny sleeves and then top loads. Then into the 3 row super shoebox size white box. Some of the really old sets you can use the 2 row box since there are fewer cards in the set.
I start the box when I decide to start the set, although I do not label the box till I am sure I have the right size box for the set. So the box can sit nearly empty for quite awhile or fill up fast depending on how quickly I acquire the cards.
I store all of my sets in xxx-ct boxes. When the set is complete I put a zipper bag over it and tape it closed so no air can get in or moisture. Those are stored in boxes put away and never looked at again.
Binders are too time consuming and expensive and take up space.
I also keep them in boxes. However, I usually trade them off after I build them. It's something about the adventure. Once the adventure is older, I'd prefer to look at it occasionally, then trade it off. Saving them seems weird, I guess. They are there, yet you never look at them, and can't display them. Cards are like mini-posters to me.
I will, however, change my stance as I complete these 99 Century Legends sets. I will keep them, and only either sell them as I reach old age, or pass them to my son, be he respectful and wise.
I only collect the base Topps set every year, including the insert sets. The current year goes into a binder. When the new cards come out, I put the old year into a 900 ct box and store these boxes in a waterproof storage tote.
I do this so that I can really appreciate and look at each card as I put it into the binder. Throughout the year, I look through it and have friends/family look through it if they are interested. When the new series 1 comes out, I replace the old with the new and get to enjoy them one last time before boxing them up for storage and/or for future reference.
Completed sets I give away to my nieces and nephews,..I seal them in count boxes with tape so they can never open them,..lol
My incomplete's I keep close,.checklists and a group stack,.and then hopefully I'll be able to find the set somewhere !!