This probably sounds completely non-helpful, but you'll know you don't need the training wheels when you're no longer using the training wheels.
I'm sure you're probably tired of the non-helpful "don't use training wheels" as well... here's the problem with training wheels.
Any two wheel, in-line vehicle (i.e., bicycle, motorcycle) is balanced and steered by countersteering*; the operator controls balance and direction by turning the front wheel the direction it's falling over, or to turn, away from the desired path of travel to force it to lean in.
Any vehicle with more than two points of contact with the ground (bus, car, motorcycle with sidecar, bicycle with training wheels), doesn't; direction is controlled "normally" by pointing the front wheel(s) where you want to go.
This makes training wheels- at the surface a good idea- problematic, as your motor system is trying to learn two different sets of skills. At best, you've converted your bicycle into a quadcycle. At worst where they don't touch the ground all the time, sometimes it's a tricycle, sometimes it's not, and you're forcing your brain to switch modes rapidly, making it harder to learn, not easier.
There's a video on YouTube channel "Smarter Every Day" with a backward steering bicycle; maybe you've seen them at a fair or carnival. The steering is geared so turning the bars right make the wheel turn left. It is very difficult to learn how to ride, because you have to retrain your motor skills. Should you watch it, note at 1:02 to 1:05, when he attempts to ride it- the bike starts falling to rider's left, and he tries to steer the front tire back under it- causing it to fall faster. Later he tries to ride a normal bicycle, and can't at first; his brain has to switch modes. This is what you're doing to yourself by wanting to use training wheels. Smarter Every Day, Backwards Bicycle
*The mechanics of which are beyond the scope, etc; for this article, let's run with the belief in magic. Or, Countsteering 101