Welcome aboard! Do you have a name? As far as blades are concerned, you will hear different responses from different people. I agree with Mark, you should probably start off with the Merkurs as they are the best combination of sharpness with a "forgiving" blade while you learn to hone your technique. As a rule, I always change my blade for my Sunday shave. I usually shave 5 times a week and make 2-3 passes per shave. I know of people who shave everyday and make 3-4 passes and still manage to get 1 week out of their blade. Anything more than a week and you'll usually find that your shaves are not as close and are becoming more and more uncomfortable. So 1 blade per week is a good idea. As for the Feathers, these are very very sharp blades that are not forgiving. I would only switch to these blades once you have mastered the art of the DE (double edge) shave. You should be pretty good in 1-2 months. If and when you feel confident to try these razors, you will find why many regard the Feather as the best razor available. Just be sure not to use too much pressure (good idea when DE shaving with any blade) with this blade as it will cut you. Hope this has been of some help. If you have any more questions, feel free to write. Once again, welcome aboard and don't be a stranger.
"Better to keep your mouth closed and appear a fool, then to open it and remove all doubt." --Mark Twain