roofing

I am wondering about the significance between 30 and 15 pound roofing felt? Given the choice, would money be better spent on high quality shingles or roofing felt? Seems these days many are high on the membrane method for valleys and under the first course areas. I live near Davenport Iowa. Not to worry, I am far from the raging Mississippi River. On average, we don't have alot of heavy rainfall or snowfall. We do seem to have our fair share of windy conditions though. I am trying to figure out just what materials to use without going into an overkill area. Any help would be greatly appreciated. JAK

12 year old skylights. Always leaked, fixed by contractor but leak came back. Roof redone - this part does not leak. Looks like joints around glass and edges. Flashing allright. Top edge only and mostly in heavy rain. Anything we can do other than caulking? Any tips for caulking? Anything would be appreciated!