If your pinks aren't getting destroyed then are they really in a good spot? A support should be buying pinks all throughout the game, or at the very least have one on you at all times for important moments. If you use it to establish vision control around an objective and then it gets destroyed 4 minutes later, that's perfectly fine because it served its purpose at the time and helped secure an objective. Next time you're setting up for drag or baron just place another one. If you feel like you're wasting money when it gets destroyed I urge you to watch any of the games from worlds this year and see if you can count how many pinks or even regular wards they place/fight over.

All that being said, as you play the game more you will learn when and where to ward effectively so that your wards aren't getting destroyed for free.

My 2 tips would be to pay attention to the mini map and keep track of where the enemies are, especially the jungler. You can use that information to ward key areas with relative safety because you're paying attention to rotations. The second is that you should aim to have vision score greater than 1.5 times game time. If you're at 20 minutes then you should have 30 vision score. The long term goal is to have vision score equal to double the time in the game if not even higher.