Different wines mature at different rates. Some are ready and are best as soon as they are bottled; others require various amounts of time to mature to where they are best. The best red wines often need 10 years or more before they reach their peak.
How long it takes before a wine begins to decline also varies. In general with kits, the faster it is ready, the less well it will age. Many years ago when I made wine from kits, I found that the fast "ready in 4-6 week" kits got better if aged 3-6 months, and started to decline after a year. Might be different now, but set aside some bottles and test for yourself.