If you don't have anything else to spend stamina on then go for it. I know for myself I want to be able to spend stamina on the current event, as well as manyus and dragons. I will occasionally refill stamina with a FG, so in that way it doesn't make sense to spend more stamina than you could buy.
I think I've three medaled every reissue I've played since I started or close to it, and I can tell you exactly which maps on the regular campaign I have not gotten three in yet, so I understand the compulsion for perfection. There's just a limit to how much I'm willing to spend on achieving it.