At lease renewal there is an opportunity to potentially negotiate not just the rent, but all the terms of the lease.
That said the courts will primarily grant a lease broadly based on the expiring lease and if there are substantial unagreed changes to the terms then there is likely to be compensation to the affected party.
Over the last 10 years or so there has been an increasing tendency for leases to be granted outside the security provisions given by Sections 24-28 inclusive of the Landlord and Tenant Act, 1954. In essence the landlord holds the upper hand in a strong market where the tenant has no right to remain in occupation after the contractual lease end date.
In these circumstances a tenant, particularly, needs to consider his options early, so that he is not negotiating at a considerable disadvantage with his landlord at the lease end date. If the landlord is going to require unreasonable terms, unacceptable to the tenant, then the tenant will have no option but to accept or vacate. If the latter, this has to be planned for.