We have already established Gohan may as well be aware of the limit, though.1. Gotenks defused few seconds after he said he will take care of Freeza.Gohan should've told Goten and Trunks to fuse against to fight Freeza until Goku/Vegeta arrives.
I've double-checked, to be 100% sure: Goten and Trunks, back in the Buu saga talk openly about the limit with Gohan present. Buutenks specifically mentions to Gohan the window of time and that he had to wait before Goten and Trunks could fuse again. So yeah, if you think Gohan remembers that exchange, Gohan should theoretically know about the Fusion one-hour limit too.
Okay, I may have actually worded it poorly: we still know Freeza can't suppress his ki in a perfectly feasible fashion because he still uses his restrained forms. It's more like I can't see why he would suppress himself in the first place, even if he could.2. Freeza CAN suppress his ki in his First Form even back in the Freeza Arc.not to mention this is the guy who have his 50% Full Power,70% Full Power etc.In RoF,he trained so much that he even learned how to sense ki.So even if you don't believe,it shouldn't be impossible for him to suppress his ki as well.





