Before you go to the bottom to rage, give me a moment to explain why I think this could be beneficial to OOO and players in general.
There are many people who outright hate temporary items, even useful ones. That's one of the reasons you barely ever see someone with the Trojan head. The only question is, would the short term money "everyones money" outwight the long term "Nolifer money".
For example, I never spent a single spark of E on a slot upgrade - and quite frankly, I just don't see the need to change that. Accessories are only useful if you have a slot for them, so I don't have to spent Orbs or time to craft them. Which could again be more money, as Orbs are freaking rare.
Now let's say a permanent Accessory Slot would cost 2700 - 18 months worth of 30 Day-Upgrades. Instead of being a gimmick for those who play several hours every day it would become something people start working toward. Everyone could benefit from an upgrade without being afraid of having wasted money because they didn't find the time to play their worth of money.
Also, if we stick to an 18 month price for a perma, a full set would cost 14,400 E. Right now only a certain number of people bother buying Upgrades - if there was a permanent solution, people would sooner or late get around to buy them. That would be 14.400 E that OOO would otherwise not get from people like me. That, PLUS the Orbs neccesary to craft some of the better accessories and increased interest in accessories in the AH.
Finally, there's one more thing I want to stress here: 18 month worth of upgrades equals more than half the time Spiral Knights EXISTS until this day.
What's so important about this fact? First, few people play for such a long time. Some play a few month, pause, get back a week and pause again. Thing is, those 18 months worth will rarely be achieved. Further more, most of those who sporadically return won't buy upgrades for "testing the new content", even if they did before. To get 18 months worth of upgrades from a single player is most unlikely in the first place.
While it is true, "renting" Slots is a good way to leech money from those with enough of it, changing this custom could hold far higher profits.
EDIT: When I say "Accessory", I mean "Trinkets". got them mixed up, sorry.
Well argued.