How long can you run good?

[77rules]

Hi all,

Been searching for the FAQ, can't find it. If you know where it is, please direct me to it. If there's no FAQ, I have a few questions:

What is the highest, sustainable BB/100 one is likely to have at 2/4?
How long does a "good run" of cards figure to run (in hands)? 5K? 10K? 20K? More?
Dito for bad.

Also, how long was your longest run of good/bad cards?

Background: Just looked at some stats for my 2/4 play. I've got about 40K hands registered. Overall, I'm about 2BB/100. In the last 20K, I'm about 3.8BB/100. I'm wondering if this is a fluke, or if it's time to move up.