I had one clone in flower for along time. I pollinated it a twice. After the first set of seeds was done I harvested them and kept it growing. It kept growing calyxs. So I pollinated it again. It eventually just died. It stopped producing new calyxs, the leaves turned all brown and it died. Shitty thing is, is that the last batch of seeds on it were still green when it died. I was hoping to atleast finish those ones, but it didn't. I just tried to germinate a couple of the immature seeds from the second attemp and it's about 50/50 for germination. So i guess it isn't a total loss. So in my experience they eventually just die if kept in flowering.
ETA: Maybe some others have had better luck then me. Maybe I did something wrong. I don't know. But mine died when kept in flowering way after it's expected life.