Is it harmful to veg a long time?

How long can I hold a plant in veg in 4 gallon buckets without doing any harm? Thanks

I kept a mother plant in a 5g pot for over a year on a 20/4 light cycle.. Didn't seem to do any harm..
She got huge..

You can hold a plant in veg for years. The main issues you’ll have will be getting root bound, and the plant just bushing out and becoming unruly. You’ll need to prune it regularly. After about a year, I like to take new cuts to “refresh” the plant and get rid of the old one. The other option would be root-pruning and/or transplanting. I’ve always had more success taking cuts and “refreshing” an old plant than keeping the old plant itself. Trying to keep an old plant alive in the same pot for several years can be difficult.