In general, it is best to treat your roof once per year. This prevents the moss from getting established. If the moss is allowed to grow for several years, it acts as compost for new moss to start if it's treated only and not removed.
It depends on how much moss and other debris you have on your roof. It is better to treat if your moss problem isn't too excessive.
Your roof can be treated any time of the year, but fall thru spring will be the most effective. This is the time of year when the moss is growing so it will take up more of the treatment.
Sealing concrete serves two purposes. First, it keeps water from seeping into the pores. When the water freezes, it expands which causes your driveway to begin breaking apart faster. The second advantage is that a sealed driveway stays clean longer. The same pores that allow water in also give algae a place to grow.
This varies depending mostly on how many trees you have surrounding your home. If you have mostly deciduous (leafy) trees then once per year after the leaves have fallen is usually enough. Evergreen trees tend to drop material in the fall and spring so twice per year is best in this instance.
Yes we are a specialty contractor with a bond and carry a $2,000,000 insurance policy.