Boils getting big...How big can a boil get?

Huge! An abscess is a tender mass generally surrounded by a colored area from pink to deep red. Abscesses are often easy to feel by touching. The middle of an abscess is full of pus and debris. http://www.webmd.com/a-to-z-guides/abscess#1.
Need not Know. I would not go there...In terms of running your own boil experiment. The skin infection can get out of hand and if not lanced will continue to get worse....Ultimately leading to a systemic reaction (fever, blood infection, hospital on IV antibiotics, etc). Get to an er, urgent care, or your doctor's office.