Question about the "old" Quintessential Wizard

[RebelAngel]

Hello I got a question concerning 2 feats in the "old version" of the Quintessential Wizard:

Imbue Weapon and Imbue Weapon Strike

Question is: how long does the weapon "stay charged" with the spell that i put on it...?

 

[Iskari]

It seems as though they stay charged until the spell is discharged. There does not seem to be any sort of time-limit listed.

This is how I as a GM would rule it.