"After the commencement of Companies (Amendment) Act 1996, a company cannot issue any preference share which is irredeemable or is redeemable after the expiry of a period of twenty year from the date of its issue"
Its clear from above statement, that maximum period for redemption of preference share is twenty year.
If the company has issued redeemable preferance shares then the company should redeeme that as per terms and conditions of issue and if the company has issued irredeemable preferance shares then the company should redeem it with in a period of 20 years from the date of issue