Concern ... let's call it #1.5, The Treadmill The short answer on this is that any temporary purchase is only going to be a realistic option for endgame players. Anyone who still needs to cert roles, weapons, or vehicles will be hurting their progress too much by putting certs in something that wears out. That makes it vitally important that these be sidegrades to the free option. Not "give up a token benefit for something better", but a genuine "all the certs in the world and I'd still stick with this sometimes" default. The fact that you have multiple tiers already makes it sound like that won't be true. You can't have multiple tiers and still call everything a sidegrade, unless you're also ramping penalties up with it. (I've never seen anyone prefer nanoweave 2 to nanoweave 5.) If you can make the default good enough that players are happy to pretend this system doesn't exist for a while, you'll have a viable cert sink for the high levels. But if implants are something people defer their Lightning upgrades in order to get, they will do it and then be unhappy when the power wears off. That's what you need to avoid.