The limits, I think, would depend on column length of your enlarger, and your own determination as to what you think is an acceptable print. There are many factors that play into what an acceptable print is, starting with the negative itself. Is the negative sharp enough to support much magnification. Is the enlarger stable and vibration free. My personal experience is, some prints look wonderful at 5x7 or 8x10, but look crappy at 11x14 or higher. Also, what size negative are you enlarging with the lens? I use my 135 to enlarge 6x6 and 6x9 alot of the time, and my 90 for 35mm. If I want larger than 8x10 then I use the appropriate lens for that negative, a 50 for my 35mm film, 90 for medium format, and my 135 or 150 for 4x5.
Does that help at all?