Watch this...
https://www.youtube.com/watch?v=P0CLPTd6Bds
Finally, somebody actually tested lens durability with and without filter "protection". The upshot is...
- Filters don't provide significant protection in a lot of cases. After all, it's just a thin piece of glass!
- Lenses are a lot tougher than you might think. And, worst case, lens front elements can be replaced.
- In some cases where a filter didn't break, the lens was damaged anyway.
- A "protection" filter might be a good idea in certain situations, such as shooting in a sand storm or at the beach where there's sea spray.
The lens hood and lens cap do a better job of protecting a lens, than a filter ever could. I virtually always use the hood when shooting and never store a lens without capping it.
Yeah, I've got "protection" filters for most of my lenses (multi-coated B+W and Hoya). They're stored separately in my camera bag until actually needed... which really isn't very often.
And, yes, I often shoot in really nasty, dusty conditions, and have to do fairly frequent cleanings...