If all you care about is the bottom-line, regarding balances being updated for the latest open period, then you can simply create 1 large journal and import->post this one journal.
Otherwise, I'm pretty sure, you will have to open each period and import->post these journals to the correct period.
Once, all the 5 years are done, you will most likely have to run REVAL,TRANSL for each period.
NOTE : you need to make sure you have currency rates defined for these 5 years worth of journals, otherwise you won't be able to run REVAL & TRANSLATION.

That's just my opinion on how you "could" handle the situation.