USCIS_Pidit bro, I think it doesn't mater how long you can work while in CPT. One thing I know is if you work on FULL TIME CPT for more than 12 months, you are ineligible to apply for OPT. But, if you work on PART TIME CPT for any number of time, it will not affect your OPT application. I think the same applies for H1B as well.