SE said with a Warning that you can only change your Appearance Once, and you can only have one Fantasia Potion...

I got one early for being a 1.0 player. The Free Trial is ending in 6 more Days, so I'm paying for another Month Sub which will get me another Fantasia Potion. But because I can't have 2 at once, I was wondering if I can use the Fantasia Potion now to Changed Appearance, then get another one as Veteran Reward and changed it again so it doesn't get wasted?

I want to make sure though since SE strictly said you can only do it once. So meaning, I either won't get another one if I use it now or the 2nd one will not work at all? Anyone know? Thanks!