Make sure it's not expired. When you open it, you should definitely detect a vinegar smell, which will indicate it's full-strength and ready to go. Before we knew better, we used old caulk once and it shriveled up after a month or two of use.

White 100% silicone

What's the best caulk to use on a bathtub? I've had to recaulk basically every year due to mildew. Thoughts?