Winter survivors

I grew a variety of Stock called East Lothian Legacy from seed this year and was rather disappointed that only a few of the plants flowered during the summer months as I had expected. However, now the weather has begun to turn colder some of those remaining plants have started to flower just as I was on the verge of disposing of them! The flowers are of the single variety as opposed to the doubles of those which flowered earlier and have a stronger fragrance. This is a variety which can be sown in late summer and overwintered in a cold frame so I'm hoping that the mature plants will survive.
I usually sow Sweet Williams every year as a biennial and pull out the old plants after they have flowered. A neighbour, however,tells me that he leaves them in and that they flower the following year.
Are there disadvantages in leaving winter survivors in place rather than sowing fresh seed each year?

 

I suppose if you leave them in you have to keep them weeded and there is always the chance the frost will get them.

I have planted Stock this year in my cutting flower bed, but I potted them up a couple of weeks ago as I thought their survival outsede may be dubious.

 

Not quite sure where to post this, but seeing as this thread is dedicated to "survivors", I thought here might be appropriate.

The only plants I've brought in under and placed under far end of car port are fuchsias of which I am rather fond. How often do they usually need watering, please?

Thanks...