First thing first, bustabit is a legit site and it is not specific to them. If you create a similar algorithm yourself and try that then also the probability to having a red streak on a certain multiplier is mathematically found but that is again a probable outcome  or the most commonly seen outcomes. It may not be the same when you play and in rare cases you might find that the outcome is not close the calculated result.

I have tried the Seuntjie's dicebot !odds command on Primedice and Stake chatrooms. It gives you an idea of when the red streak will come but again it is not absolute. But I am yet to see any commands from Seuntjie for how long the streak may be.

This according to me dependent on your luck. You may get a nice green streak on a high multiplier (be sure to stop when this happens and cash the profit) OR, you may get a huge red streak on a very small multiplier.