I used to remove them during tiling. So i'd tile to a height around the room, or on one wall, and then as I tile above that I'd nab the spacers from the first few square meters and re-use them on the next few.
Though that'll work with ceramics, and on floors using any tile, you might find you need to keep using them while the adhesive goes off if you're using heavy tiles, or large ones. And those are being fitted a lot more now than when I used to tile.
I used to hate pulling them all out before grouting, and I'd never grout over them, there's always one or two that cause big problems or you chip tile edges trying to force them out with something. So I got used to waiting for the adhesive to go off enough to carry the weight of the tile and simply re-use as many as I could / would dare.