It will probably take 9-14 years from the time the seed sprouts before your Lychee ever produces fruit. And once it does begin producing fruit, there's no guarantee that the fruit is going to be as nice as its parents, or that the tree will produce fruit reliably. For this reason it is not common to grow Lychee from seed. I do have to say though that it is very easy to grow Lychee seedlings from the seeds.

Lychees are not considered to come true from seed, though from what I've heard it's better with Lychees than many other temperate fruits (i.e. the offspring will probably not be too different).

A lychee tree is self-pollinating, though I heard an expert say in a video that if there are two different varieties they will produce a greater number of fruits. That is not really the issue though because Lychees by their nature are generally not entirely reliable producers; there will just be some years where there is very little or no fruit on a particular tree. Different varieties are much better than others in this regard, but there are trade-offs. If you bought your lychee fruit from a store, the variety is most probably Brewster, which [when mature] might not produce about every 4 years.

If you want lychee for the fruit it's better to buy a grafted cultivars....from seed it's a very very hard bet

i have 5 (left), i killed a couple.

one of them is outgrowing a 3gal pot, and wont stop producing leaves.

i hope it will be that way with fruit.

the others are pretty slow-going... in the spring i will re-pot them

and figure out what soil i was using... LOL

i did a lot of reading on them, and i think they must need (or like very much) 1 particular kind of Mychorizzal fungi... the literature i read seems to confirm that, and i think that is what is happening with my plants.

none of mine were growing well, until i put 1 in the ground, and another in a 3gal pot, then gave them worm-tea and fish emulsion... Now those 2 are doing really good. The ones in small containers still are very slow, and ive heard certain fungi and bacteria do not grow in small containers due to temperature variations.

I plan on having 2 in the ground, a couple of feet away from each other, pruned at different heights. i plan on grafting a couple of varieties onto them as well, but, i will probably leave a branch or 2 on each tree just to see what they taste like - at first anyway.

So, personally, i would keep them in oversized containers, and get some mycorrhizal fungi, worm-tea, or compost tea, and maybe some fish emulsion too.