In my experience, a Gilette shaves cleanly (no cuts and inflamed follicles or ingrown hairs) for the first couple of times (when it's very sharp), then causes a few cuts unless you're very careful for the next 5 shavings or so, and from then on becomes so dull that it becomes quite hard to cut yourself unless you try to or move the blade along its length. A single Gilette blade lasts me several weeks to 2 months. It's only during the 'transitory' period that you need to be careful, and not apply too much pressure. When the skin becomes very red and irritated, it's time to ditch the blade.

Like someone mentioned above, for me the trick is to shave first along the grain, then lather up again, and then against the grain. That prevents redness, cuts and inflammations much more than using a fresh blade.