I've had a grapefruit tree for 24 to 29 years. I planted it as a seed. I planted several others, which sprouted, but they got something like mealybugs and all of them died, except this one (which became free from the pest after a while).
We use my tree as a houseplant. It's never been outside, to my knowledge.
My tree grew very slowly for the first few years (it was just a few inches tall), but it eventually got significantly larger.
On 4 June 2020, I noticed it had its very first bud! I've been hoping it would flower (and fruit).
The bud isn't facing the window. My tree is in front of a south window. As far as I know, there's only one bud, so far. It's been in front of this window since about 2014 or so, but had less light before then. It's had more light for two or three years, since we removed trees that were in front of the window.