How to validate the result of a Case

Validating the result of a Case

I'm getting the interval between two dates in days, I want to validate if the result is greater than 120 days, is it a better way I'm doing?

DECLARE @DataInicioVigencia datetime; -- ='2018-11-30T00:00:00'; 
DECLARE @DataInicioVigenciaProgramada datetime = '2018-11-30T00:00:00'; 
DECLARE @DataAdmissao       datetime = '2018-07-01T00:00:00';  

select
   CASE 
     WHEN isdate(@DataInicioVigencia) = 1 AND 
          (  ABS(DATEDIFF(day,@DataInicioVigencia,@DataAdmissao)) > 120 ) then 1
     WHEN isdate(@DataInicioVigenciaProgramada) = 1 AND 
          ( ABS(DATEDIFF(day,@DataInicioVigenciaProgramada,@DataAdmissao)) > 125 ) then 2
   ELSE 3
   END as 'PRAZO'
from FUNCIONARIOS

--mostrar o cálculo
select ABS(DATEDIFF(day,@DataInicioVigencia,@DataAdmissao))
select ABS(DATEDIFF(day,@DataInicioVigenciaProgramada,@DataAdmissao))