they were considered good back in the day, but realistically, because of the design of an incandescent bulb, they can only coat the outside of the bulb to give any kind of spectrum at all. problem is that the coating burns off rather quickly, as anyone who has ever had an incandescent blacklight that was used on a regular basis would remember

florescents and cfl's on the other hand, use all kinds of good stuff inside the tube that gets excited with all that energy flowing though there and because a much more stable spectrum. at least for a year or 2. i change bulbs every 18 months, whether they are burnt out or not.