Questions about UVB treatment

Hi, my girlfriend Sara has had psoriasis for about 10 years and has recently started trying a small handheld UVB light. We are considering buying a Philips 5 tubes "canopy" (we live in a very small house, we don't have space for a 9 tubes one), because the treatment of the whole body with this small light takes way too long everyday (about 3 hours in total at the moment, but by the end of the treatment it will be about 5 hours a day!). We have a few questions about UVB treatment: 1) Shall she continue on a piece of psoriasis after it has been "burnt" by the UVB? (when the skin in that area becomes "more brown" and doesn't have psoriasis anymore) 2) After doing a 6 weeks treatment, can she continue doing "maintenance", and how many times a week is that? Would it be with the maximum duration that she did the treatment for? (7min30). Or shall she stop completely for a certain duration, before using the light again? 3) For the scalp, will the UV canopy be enough or will she still have to use the handheld light with the comb attachment? (it takes 2 times 20 minutes every day, just to do the scalp). Thank you for your help and for sharing your experiences :-)