Yeah, you should probably sell it before Valve comes out with new contracts or something and slowly lowers the price of older skins. I'm not saying to ABSOLUTELY do it, that's still your choice, but I would from experience.
I made the horrible choice of keeping my Factory New Woodland Warrior that I unboxed(I think that's what it's called) for a little longer because I wanted to use it. It almost sold for 9 keys at the time, and I sold it for only 4 keys. That's less than half its profit from before. So, if you're want a bigger profit, then I would recommend selling the Flash Fryer. But if you want to keep it for sentimental value, then go ahead. I still got a profit out of the selling by the time I was done with the Woodland Warrior, so don't let that one specific scenario decide this entire thing.
Nonetheless, this is all your choice. Do what you feel suits you best, and go on from there.