Vulkem 116 Polyurethane Caulk - The Best
I first used this product more than thirty years ago. They still make it - their is a reason for that - This is the best caulk I have ever found. Big box and local hardware stores don't usually carry it - you will have to track it down at builder and construction outlets.
For me - this is a 'forever' caulk. Be careful this stuff will (nearly) permanently stick to your hands - Acetone, alcohol, or MEK won't remove it.... takes weeks to wear off.