Until 11ish usually.
I'll give you my tips: Not sure if you're alone or with family/friends- but everyone needs to get there early and wait at a podium. Just like always, people love lines. So if there is an empty podium with no line, go to it. A TM will be at every podium (most will have 2 per during busy times).
Quick note: Make sure you have towels from the pool of the hotel youre coming from the day before you go to VB.
If you're at the front of the podium, have your party occupy both sides- that way if there's 2, you're covered without a line splitting and you being unaware, you'll also get your party in twice as fast. Everyone put their sunscreen on there and take off shoes, cover ups, etc 2-3 mins before opening and give them to the "lounge chair guy/gal" or whoever has the longest legs/moves the fastest. Everyone except the LCG goes straight to krakatau coaster. The "LCG" will fast walk to the sitting area (right in front of the volcano or wherever you want). Throw the towels on however many chairs you need kick off their shoes and then head to Krakatau as well. Don't do lockers- don't even mess with them this early.
If you do this, you should get 2-3 rides on Krakatau before getting out. Even during busy season. I've gotten 6 before without getting out of the canoe- and that's with a (then) 5 year old in tow.
Everything else is personal preference. But you should be "Krakatau'd out" and way ahead of the crowd if you use that first 5 minutes wisely.