It depends

It depends on how you obtained the EAD;
1) if the alien otained the EAD as a benefit deriving from family sponsored immigration application, no limit on EAD;
2) if the EAD was derived from an employment-based I-485 application, the principal applicant can only change jobs after 180 days I-485 pending and subject to other restrictions; the derivative beneficiaries (family members) can use EAD to work without limitation.