Can't you always dive back into industry when you're past your current crop of ideas?
More likely for me, I think, is that I would develop interest in some other problem area, and just dig in to the new domain. For example, I'm always struck when I hear about the sorts of medical problems that hit people from my wife's village. I don't know anything about medicine, but it feels to me like a focused data collection project could lead to a significant improvement health outcomes.
It may be partially due to my training as a researcher keeping my eyes open to it, but it is a pretty rare month that goes by where I don't run into an interesting problem I could easily spend a year or two working productively on. Many of them don't come out of my current work or even during my work time.
The idea of running out of "good ideas" is unfathomable to me, honestly. Running out of time is very easy to imagine, though.