If I paid now I would expect that the start date would be now. But, we are talking an exchange company here aren't we. It's a question I'd want answered, preferably in writing, before I renew/re-start my membership.
Of course, the big question in my mind is, what were the reasons for allowing your membership to lapse? If it had anything to do with dissatifaction with the exchange company why buy 5 more years of dissatisfaction?