I think if soap is left without a lid on for a considerable ammount of time that it can lose some of its scent,for instance if you see people selling Old Spice shaving soap they will mention sometimes that it still has its scent,so that could be an issue.
You can get a nice sized tub in Wilkinsons for about 30p,plastic with a push down lid,i was just hoping for a twist/screw top but if i cant find anything i will get a few more of those Wilkinson tubs