You can subscribe to The Play Kits at any time—there's no need to wait until your gift ends. When you subscribe before your gift runs out, you'll keep The Play Kits coming right on schedule, so you won't miss the next developmental window.
You can subscribe right from your account. After you've signed in, click on Play Kits, and then scroll down to Subscribe Now. You'll be taken to a checkout page to add your payment details and review your order.
Once you're subscribed, your Play Kits Subscription will begin after your last gifted Play Kit ships.