Hi, welcome to GoY, do you happen to know which sp4cies you have? there are about 14 species, 3 of which may survive short periods of 32f providing they have been kept dry, but most need to be kept to a minimum temp of about 45f or above, have you fed it regularly in the summer, and if it's been in the same pot for 10 years it's quite likely to be pot bound, try taking it out of the pot to check, if it is, repot into a larger pot, it could also be too cold for it when you put it outside in the summer, especially if you just put it outside without hardening it off beforehand, do you top dress in late winter?,
use j i no3 to pot on, and from spring to autumn, use a balanced liquid fertilizer once a month, other than the above I can't think of anything that would cause this problem, Derek.

thanks for the above, the answer to most of which is, quite honestly, "no", which gives some food for thought. On the plus side, of course, it is quite nice to have it in flower in the winter. I shall follow your advice and see what happens. Thanks again, Tony

feed and water it outside more often than when its inside, maybe you should keep it out for 1 whole year just so it gets used to the new cycle.

Wlb, this plant willnever get used to being outside for a full year, it won't live long enough, all species are native to tropical and sub tropical areas, although as I said, there are 3 species which "may" survive temperatures down to freezing, if they have been kept dry, but only for very short periods, Derek.