I always use filters, and try to always use Leica filters. No matter how many times I wipe them, I can't get a wipe mark to show! Rain, dust, fingerprints, all wipe-off with ease. I too have had a couple of close calls in my 45+ years of photographing. Filters have saved the lenses for sure!
To those that seem to have "flare" problems, perhaps the use of only the best newest optics AND the use of lens hoods would help solve your problems. Aspherical and Apo are the ONLY lenses I own, besides the Noct. and the Noct. tames light sources in the image.