From BF3 blog -
DICE: it takes 100 hours to complete a kit and unlock everything
One of the most popular aspects of Battlefield 2 was its deep persistence feature, where players earned unlocks and awards as they played, and which could keep them busy for years. This returned in Bad Company 2, however, you could unlock most of the weapons and gadgets in Bad Company 2 in a few dozen hours, something which took DICE by surprise.
For Battlefield 3, DICE always stated that they were going with a much deeper persistence feature, with many more unlocks and a revamped unlock structure for weapons and attachments. Now DICE’s Alan Kertz has unveiled just how long it takes to unlock all the weapons, attachments and gadgets for a class: 100 hours.
The reason it takes so long is because unlocks in Battlefield 3 are given per weapon basis, where each weapon attachment must be unlocked for a specific weapon, meaning that players will be unlocking the same attachments and gadgets over and over again, for each weapon. Most weapons will be given three slots: one for scope, one for barrel, and one under-barrel slot for grips, bipods, grenade launchers, etc.
On one hand, the more you use a weapon, the more and better accessories you get for it, on the other hand, it might get a bit too repetitive unlocking the same thing again and again. But we’ll have to wait and see how the system works when the game ships. Or in the upcoming beta.
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If you think about it, an unlocked scope should work on ANY gun that supports it. Why should I have to unlock the exact same scope for a different gun? Its not like its welded onto a weapon. Really odd design decision.
So whats next? Unlock "ammo" for every gun even though they may share the same type? Maybe they want us to start the game with a knife? Or how about butt naked and unlock underwear, shoes, pants, vest, armor, helmet etc? They can extend the unlocks by another 50 hours this way.
Sounds really annoying not to mention stupid IMO....