Just wondering, how long?

I got this nest kit for Mother’s Day. I love it! I’ve   always loved bonsai. I planted the seeds today (5/10/2025) so hopefully I’ll get sprouts before summer but do I need to let these sprouts grow for 3 years before they even resemble a bonsai in appearance. I am almost 67! I’ll be 70 and by then I may forget everything! 
 

Your question is hard to answer. We do not know when you think it resembles a bonsai.

I grow trees from seeds and cuttings sinze 5 years back. I would consider most of them still to be saplings or young trees. Just a few, where I am aiming at small size bonsai, already introduced low movement and removed sacrificial branches I would call prebonsai. I will not call them bonsai in at least 10 more years. Quality trees from well known bonsai nurceries is seldom less than 25 years old.