I would imagine they could theoretically live forever if well cared for indoors. I am not a botanist, however. I have heard of one individual here that veg'd a Cannabis plant for 3.5 years before putting into flowering That is the longest I have heard of.
people keep bonsai-style mother plants indefinitely unless theres a reason they have to get rid of it. so to answer ur question a plant can live forever in veg inside
I didn't see any pictures, but I am sure it was a GINORMOUS Cannabush of the likes which ye have never seen