I have tried both reconditioned and compatible ep27 toner cartridges but none have the durability and performance of the original Canon brand. It may cost more but it lasts longer and produces an even tone until it runs out and, importantly, the ink does not fade on the printed document as I have found with cheaper alternatives.
Each toner cartridge does seem to last much longer than the 2500 sheet stated capacity and I do sometimes print off photographs and other documents that will have much greater than 5% ink coverage on the page. Even when the toner actually does get low, shaking the cartridge often produces quite a few more pages of printing before I need to replace it.
The cartridge is protected well within the box, which can then be used to return two cartridges to the manufacturer (freepost) for recycling.