I am with you always, even unto the end of the world. Matthew 28:20 KJV
Jesus is with you!
When will He be with you? He will be with you always.
How long will He be with you? He will be with you until the world ends.
As long as the world is here and as long as you are in it, you can be absolutely, positively certain that He is with you.
This is His promise to you.
And best of all, when you get to heaven, Jesus will no longer need to promise to be with you, because in heaven, you will be with Him forever!