Based on the requirement  we have created the WFR ,where certain conditions should get met for an email notification to go the owner before 100 days of the contract end date. So i have created the a time based workflow rule and a email alert.
Condition is 1:
1)Renewable status is equal to pipeline , next qtr
2)Next Year Status is not equal to renewed or renewed lost.
3)Renewed is true
So while creating a Rule criteria i have used the filter as : This is the Criteria met conditions i have given for 100 days .

((Contract: Contract End DateNOT EQUAL TOnull) AND (Contract: Renewal StatusEQUALS pipeline) ) OR (Contract: Renewal StatusEQUALS next qtr) OR (Contract: Next Year Status NOT EQUAL TO Renewed) OR (Contract: Next Quarter Renewal StatusNOT EQUAL TO Renewed lost))

Now when the 100 days email is sent to the owner ,their is an update done for the field SRR (picklist).
a)If SRR is YES --- then an email notification is sent for 15 /30/45 days .
b)If SRR is No ---- then stop sending email
c)If SRR --not updated with any value and left blank .

Then i need to send an email notification for 90 days before the contract end date to the owner.

1)Renewable status is equal to pipeline , next qtr --picklist field
2)Next Year Status is not equal to renewed or renewed lost.---picklist field
3)Renewed is true ---formula field make it checked
4)SRR is Blank(not updated) ---picklist field.

NOw ,
a)if the SRR field is YES and 15 /30 /45 days email to be sent .
b)If SRR is NO or Blank --stop sending the email.

Formula used is rule criteria:

AND( OR( ISPICKVAL(Renewable status, 'next qtr'), ISPICKVAL(Renewable status, 'pipeline') ), NOT(ISPICKVAL(Next Year Status, 'renewed' )), NOT(ISPICKVAL(Next Year Status, 'renewed lost')) )

Any help very much appreciated.