My male LGF died suddenly, the pair were together 6 months but never bred. The female seems fine, how soon should (if I should) introduce another male?
Yes, by all means add another partner. I would add one as soon as I wanted. Usually I keep a small cage with the newcomer in it just beside the other Gouldian's cage so that I can see and judge whether both birds are going to like each other, maybe a couple of days before putting them together.