(b) The eligible taxpayer shall maintain its qualified investment for a minimum period of five years: Provided, That an eligible taxpayer receiving repayment or return of a qualified investment (exclusive of interest, dividends or other earnings on the investment) shall within three calendar months from the date of repayment or return reinvest the repaid or returned amount of the initial investment in another qualified research and development company for a period of time at least equal to the remainder of the initial five-year term.