You don't say what you're driving. We are all assuming it's a Model 3, but there are Teslas with 400 miles range (my Model S LR) or 250 miles range (my daughter's Model X). Even then, 150 miles is not scary at all. You don't need to charge to keep the battery warm: you have plenty of extra power, and 30 degrees is not that cold. It will not take much juice to keep the battery warm and ready to go, and your battery will have enough power to do that. I live at 1500', but my gains driving down the hill are negated by driving up. It's a balanced equation.
It takes a while to gain the faith in your car and know what it can do, but you will. The next trip will be worry free.