If you exemplar more than 3 levels below the IO, you will not receive the Recharge bonus. This is one of the reasons by the lower level recipes/IO's are higher in demand, aside from the fact that you can simply slot it earlier. That particular IO counts as a Global Bonus. For Global Bonuses, it doesn't matter if you exemplar to a level before you have the actual power as you will still receive the benefit of the bonus as long as you are within 3 levels below the level of the IO.
Let's say you have a level 35 LotG +7.5% recharge that you slotted in a power you acquired at level 41. You exemplar to level 32. Even though you didn't acquire the power that your IO is slotted in until 41, you still get the Global Bonus because you are within 3 levels of the IO's level. If you slotted a level 35 IO into a power you acquired at level 20, you would still lose the bonus from it if you exemplared to 31.