Last year I planted a couple of lychee stones just to see what would
happen.
One of them germinated and grew two pairs of leaves. Then nothing. About
six
weeks ago, i.e. one year later, it grew another pair of leaves. I'm
growing
it as an indoor plant. Has anyone grown them? Is it destined to grow only
one pair of leaves a year?? Admittedly very nice leaves!

I've been growing longans in my greenhouse for a couple of leaves.

Very slow growth, not much chance of any fruit - would be my assessment.
--

I wasn't anticipating any fruit - just a nice green plant.