No, there is no time limit. JAR-FCL 1.335 states
Before being permitted to begin an approved course of training for a FI(A) rating an applicant shall have:
(a) at least a CPL(A) or completed at least
200 hours of flight time of which 150 hours as
pilot-in-command if holding a PPL(A);
(b) met the knowledge requirements for a
CPL(A) as set out in Appendix 1 to JAR-FCL
1.470;
Under EASA proposals you may not need it at all, but that could change!