Is it OK for my windshield wipers to hit the vinyl lettering?

Valid concern. Your decals will do “fine” even with the windshield wipers hitting them. However, as you may have noticed, windshield wipers can pick up dirt and scratch even the windshield. So if they scratch the windshield they will damage the lettering. That being said, you should have many years of use – even with the wipers “hitting” (just make sure they stay clean and do not wear out).

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