Using SSj3 while alive

[Kaboom]

I never before took it to mean something so... existential. Just that time is the drawback of Super Saiyan 3 because the insane energy drain ends up putting a limit on how long you can use that power. Goku's line about being able to use it only in the afterlife "where time has no meaning" is odd, though.

[Bussani]

The "where time has no meaning" line is odd, but Goku also plainly says this:

Chapter: 513 (DBZ 319), P1.2
Context: after Goku drops out of Super Saiyan 3
Goku: “Da-dammit…When I was dead, it was no problem at all…It seems that in the end, becoming a Super Saiyan 3 with a living body eats up an excessive amount of ki…”

[Fox666]

Considering a dead don't even need to eat to survive, I guess it's possible they have an infinite amount of energy, don't?

[Kroni_Hunter]

Yes, that's how I think of it. It's like Androids 17 and 18, they have a maximum ki depending on their battle power but any energy they use gets replenished instantly forever.