Radars only give bouquets, I can't see any reason to spend them if you're already >9,000 bouquets unless you know you can get to 50k using them. The achievement rewards between just aren't worthwhile (and even 9k isn't all that great if you have a pile of card reveals already). Might as well save them for a future event when you can throw them in at the beginning if you are able to get some SR-Slayers from saved e-gacha tickets. I'd rather get battles (cases & keys), exp, and gifts from rolls than wasting my stamina on radars.