For Daizenshuu followers (I'm not saying I'm one of them), it's a perfectly viable explanation to make the official numbers work. Goku's power-burst read at over 8,000, but that doesn't mean he kept that power. The artwork and printed sound effects clearly imply that he went back down to his normal 5,000.
No, you do not need to see another power-up to determine Goku went back to his normal power level. Perfect Cell versus Vegeta SSjG2 is a perfect example to debunk this silly way of thinking.
Respect another's opinion and don't act like yours is the only valid one. Especially when it relies heavily on fan made myths and speculation regarding power gaps that are not backed or supported by the Manga.