You know it is handy to have a few clear filters available in your bag. But to use them always? I don’t think so.
Why not? Because they can degrade your image a little. In particular, they can cause extra flare. Like in these images taken today by a student:
With the clear protection filter on the 50mm lens:
And a second later, without the filter:
Look at my face, under my chin, etc: the strong back light causes flare in both locations; but it is noticeably worse with the filter, since the light bounces back and forth between the extra layers of glass, thus causing degradation.
My advice is: have a filter, but only use it when your camera is in danger from sand, water (especially sea water), snow, and other such dangers.
Learn From The Pro: You can benefit from private training and portfolio reviews too: the June special ($75 per hour instead of 95 per hour) is still on and there are some slots available during days, evenings and weekends.