JoeyBike

If you take it easy, avoid sharp turns, hockey stops, and fast starts - and you rotate the wheels regularly - they will last a few months (assuming you skate regularly)

Physics. The longer you make a vehicle that slides along the ground or water, the higher you raise it (wheel diameter for skates), and the narrower you slice it - the faster it will become. Not just skates - everything trying to overcome "hull friction". Skis, canoes, kayaks, skates, oil tankers, etc. Length also generally adds to stability. By adding wheels to skates - speed skates used to commonly have five wheels - you distribute the weight of the skater over more wheels (crushing each one of them into the ground less) and you add more bearings which also serves to lessen the crush-force on each individual bearing. As you add wheels the skates become more stable and harder to turn. Conversely, skates with two wheels each are going to be mighty "squirrely". Speed skates also have TALL wheels - slower acceleration, easier to maintain top speeds and more forgiving on bumps (same as 29er bike wheels vs 26" wheels). Also, new speed skate wheels have a razor-thin profile to minimize the amount of urethane touching the grind. Hence the name RollerBLADE. Like an ice skate blade. All of these features mentioned add to speed and stability.

On the other hand, roller hockey wheels are "rockered" so that no more than two wheels ever touch the ground at the same time. The wheels are also smaller diameter for faster acceleration and have a rounder profile for more traction on tight turns. Ice hockey skates have curved blades, roller hockey skates do to. They can turn on a dime. Everything in Physics is a trade-off. Sea Kayaks are long and skinny with some sort of keel that makes them like a floating needle for improving what is called "tracking" or the ability to hold a straight line. Whitewater Kayaks are short and flat-bottomed - the river is doing the moving forward for the kayaker needs to be extremely maneuverable around rocks. Long kayaks are fast forward by paddling, short kayaks need current for fast forward progress. Long skis LIFT the skier to the top of the snow same as kayaks lift the paddler to skim the water. Longer the ski - the higher the lift and a reduction in friction.

Suspension just adds weight and not much benefit for tiny wheels. Urethane comes in different numbered hardness ratings called durometer. 75 is like a pencil eraser, 95 is like a porcelain sink. Harder = faster, softer = grip. You want a soft ride, go with low durometer numbers BUT they will wear out faster and make you work harder. Another trade-off. And since you have a skate attached to both feet, when you come to a curb or broken pavement - just step up onto it. I can actually skate on broken paved roads that give cars a hard time - because I can choose a narrow line around potholes and just step up onto uneven concrete slabs without slowing down. So suspension is unnecessary AND will rob you of efficiency by crushing every time you try to push for power.

Well, that is true. But for recreation/fitness skates (not hockey skates) you should be keeping all four wheels on the ground at all times. When you are pushing along, you don't want to look like a duck on ice. The blades should always stay parallel to your line of travel when skating straight. You push with your heel most of the time if you want good form. This also helps your wheels wear evenly. One exception is speed skating. A speed skater will bend his/her knees A LOT while stroking along, and at the very end of each push stroke they will finish with the front wheel. All the rest of the time those blades are perfectly parallel to the direction of travel. That little push with the front wheel at the very end of each stroke gives them about 5% more push than not doing it. So it is worth it if you are in a race, or practicing to race. Otherwise this should never happen on recreational skates. Keep all four wheels on the ground. There are videos all over YouTube illustration a good push stroke.

One last reason why inline skates are more practical for commuting than quads, skateboards, or longboards. Because all four or five wheels are in a line on the frame, the frame acts like a bridge when crossing expansion joints, cracks, train tracks, whatever. You could roll over a 4 inch expansion joint gap and not even feel it. With quads and skateboards both front wheels are going to drop into that expansion joint and send the skater flying. Also quads and longboard wheels are WIDE, so they are more likely to hit some debris and stop short, again sending the skater flying.

OK...hope that helps.