I feel like you're having to get permission from your current t to do this. You said earlier you "only have to go every second week". Is current t dictating how often you can/have to see this other t? And you feel the need to ask if it's okay if you see the new guy before he leaves. You don't need his permission to take care of yourself. He's the one going away for three months. You can see new guy as early as and as often as you feel you need to (I know you said money is an issue). I just worry that there's some power dynamic going on with your current t that is harming you.