Destiny Points aren't meant to be used in an adversarial relationship between the GMs and the Players a la upgrading checks. They are meant to be powerful narrative tools that introduce elements that didn't already exist previously into the scene, so long as the new elements aren't completely outrageous.
For Example:
The GM finds that his preplanned Minion groups of Army Troopers in a forest outside an Imperial base being mowed down with ease by the PCs. This particular scene is meant to be battle that the PCs could not win. Flip a Destiny Point, the PCs are ambushed by deadly Stormtrooper Minion Groups from all sides with a Stormtrooper Sergeant leading them. Vice versa, the PCs could use a Destiny Point themselves to introduce a fallen tree trunk that they could use for cover.
The constant back and forth of upgrading checks doesn't add to the quality of the story that is being told. It shows a lack of willingness to be creative in a game that practically requires both Players and GMs to be creative in order to play the game in the spirit it was intended to be played. GMs, Players: if you find yourselves in a session where the constant back and forth is a bore, then pause the campaign (not necessarily the current session) to brainstorm various ways the Destiny Pool can be spent other than upgrading checks. Communication is key. Don't let the back and forth upgrading bring your game to boring grind.