Whilst not strictly a Photo Lab tip, this is a photographic tip in general and does come in useful as I found at the Shoreham Airshow Press Day when juggling with my cameras I managed to drop one….
Thankfully because it had a UV filter over the lens I only have to buy a replacement filter and not a replacement lens! UV and clear filters can be used for this exact reason, they also help with keeping your lenses clean and intact as you only have to clean the filter and avoid scratching the surface of the lens.
Of course there are always arguments for and against, Wikipedia has more on the subject.