Thank you.
Then, the mintage is reset for each reward in two INPUT.
Each time this happens:
Would it be better to make a transfer and collect the two amounts in a single INPUT, to obtain better reward results?
You can, but the reward will wind up just about the same if you combine them and gain one pos reward, compared to leaving them split and gaining two pos rewards for two inputs half the size.
I think the intention behind the pos splitting, which is inherited from Peercoin, is to help ensure that there are always a healthy number of inputs in the network that are eligible to mint blocks (promoting the chance that pos blocks are minted regularly). So by allowing it to split, you are helping the network and getting the same reward over time. ((related discussion can be found by googling similar topics raised by the Peercoin community.))
I think it does make sense to occasionally re-combine inputs as you suggested, but only when some individual inputs in your wallet have become so small that you think you will have better chances of minting a block if they are combined.
It may even be possible to modify the client to split and re-combine depending on different conditions than the default - Maybe the emc devs could add some user-configurable options for how splitting is handled in future? I think that would be a nice option.
Anyway, as the reward should be about the same, I wouldn't bother re-combining manually unless you have many many small inputs.