Are you sure that floppiness wasn't due to lack of sufficient bright light? They need a bright position, or they put out over-extended growth which then goes floppy.

You can water them liberally during the summer growing season, eg soak em once a week. Need to be in very well drained soil through. But barely water at all during the dormant period in winter, only if they look like they really need it, or are getting roasted by your central heating.

This is general advice for most desert cactus, there are exceptions.