you can veg forever if you want. that is pretty much what you are doing if you are keeping a mother plant to take clones off of. usually people only veg to grow to a desired shape/size before flowering.
Won't an 80-day veg become rootbound even in a 5-gallon bucket and grow through the second floor by harvest?
Eventually yes. But you could re pot it. If it was veged for 80 days you would get a huge harvest off that. Put it in a small garbage can or something.
There is no too long to vegging, but it just depends on what size pot you have her in.. If you have vegged her for 80 days I hope you have been transplanting her up into bigger pots along the way.. Girls will double to triple size in flower.. A good rule of thumb is 1 foot for every gallon.. I'm not sure how big yours is, but I have a girl about her age.. Mine is actually at 74 that I just moved to flower today.. She is 2'1" right now and I've already been told that a 2 week vegger had a decent size so I expect her to end up between 4 to 5 feet tall.. That being said I have her in a 5 gallon smart pot to make sure her roots have room to grow.. Hope that helps..