H1B visa extension drop box in admin processing

[h1bdropboxap]

My H1B visa extension via dropbox case has been in status "Administrative Processing" for a day now. What is the longest time the case can stay in this status? If it is a 221(g) case, will they inform us about this? Can it stay in administrative processing for a long time without 221(g)? Does anyone have experience with their status being "Administrative Processing" in the Mumbai Consulate dropbox this December?

Any replies will be greatly appreciated!